There is no weight restrictions on PA Antique tags. I had a M35A2 and currently have M925A2 with PA Antique tags.
Who told you that you could not go over 10K?
PA Antique Vehicle Fact Sheet
PA HMV Fact Sheet
Historic Plates
You can get plates for an antique Bus or Truck with the MV-11 form.
This information is from Title 75 of the Motor Vehicle Code:
§ 1340. Antique, classic and collectible plates.
(a) General rule.--Upon submission by a vehicle owner of information satisfactory to the department that a motorcycle or motor vehicle is an antique motorcycle or motor vehicle or classic motorcycle or motor vehicle or collectible motorcycle or motor vehicle, accompanied by the appropriate fee, the department may issue special plates for the motorcycle or vehicle. The special plate for antique motor vehicles, except antique motorcycles, shall bear the designation "antique vehicle." The applicant shall provide photographic proof in a manner specified by the department to demonstrate the condition of the motor vehicle. No annual registration fee may be charged for antique, collectible or classic motorcycles or motor vehicles. A holder of the special plates may obtain replacement plates bearing the designation "antique vehicle" upon payment of the appropriate fee.
(a.1) Vintage registration plates.--In lieu of a special plate issued under subsection (a), the owner of an antique or classic motor vehicle may request permission from the department to display a vintage registration plate from the model year of the motor vehicle. The vintage registration plate shall be:
(1) Provided by the motor vehicle owner.
(2) A Pennsylvania registration plate issued between the years 1906 and 1976.
(3) Legible from a reasonable distance.
The applicant shall provide information as the department may require for processing the request and a $75 application fee. The department may deny a request to use a vintage registration plate for cause.
(a.2) Historic military vehicle plates.--In lieu of a special plate issued under subsection (a), the owner of a historic military vehicle may be issued by the department special plates for the vehicle which shall have the same force and effect as antique or classic registration plates. The applicant shall provide information as the department may require for processing the request and a $75 application fee.
(b) Use of plates.--It is unlawful for any person to operate a motorcycle or vehicle with antique, classic, vintage, collectible or historic military vehicle registration plates for general daily transportation. Permitted use shall be limited to participation in club activities, exhibits, tours, parades, occasional transportation and similar uses. Occasional transportation shall mean no more than one day per week.
(c) Definition.--As used in this section, the term "historic military vehicle" means an antique or classic vehicle, including a trailer, that was manufactured for use in any country's military forces and is maintained to represent the vehicle's military design and markings accurately.
(May 30, 1990, P.L.173, No.42, eff. 60 days; Apr. 29, 1994, P.L.148, No.25, eff. 60 days; Dec. 20, 1995, P.L.669, No.75, eff. 120 days; Dec. 1, 2004, P.L.1767, No.228, eff. 60 days; Apr. 12, 2012, P.L.227, No.25, eff. 120 days; July 2, 2014, P.L.988, No.109, eff. 60 days; Oct. 24, 2018, P.L.645, No.91, eff. 120 days)
2018 Amendment. Act 91 amended subsec. (b) and added subsecs. (a.2) and (c).
2014 Amendment. Act 109 amended subsec. (a.1)(2).
Cross References. Section 1340 is referred to in sections 102, 1786, 4703 of this title.
§ 1340.1. Street rod plate.
Upon submission by a vehicle owner of information satisfactory to the department that a motor vehicle is a street rod, accompanied by the appropriate fee, the department shall issue special plates for the vehicle which shall have the same force and effect as regular registration plates. The applicant shall comply with all laws and regulations pertaining to registration including the payment of any additional fees.
(July 10, 1981, P.L.250, No.82, eff. imd.)
And yes, you can drive them at night with antique tags. So long as the vehicle meets the current PA lighting standards.
§ 4303. General lighting requirements.
(a) Head lamps.--Every vehicle, except trailers, operated on a highway shall be equipped with a head lamp system in conformance with regulations of the department. The regulations shall not prohibit a bus from being equipped with devices used to carry pedalcycles on the front of the bus.
(b) Rear lighting.--Every vehicle operated on a highway shall be equipped with a rear lighting system including, but not limited to, rear lamps, rear reflectors, stop lamps and license plate light, in conformance with regulations of the department. If a vehicle is equipped with a centrally mounted rear stop light, a decal or overlay may be affixed to the centrally mounted rear stop light if the decal or overlay meets all applicable State and Federal regulations.
(c) Turn signals and hazard warning lights.--Every motor vehicle, except motorcycles and pedalcycles, and every trailer operated on a highway shall be equipped with a system of turn signal lights and hazard warning lights in conformance with regulations of the department.
(d) Identification, clearance and side marker lights.--Every motor vehicle, trailer and combination operated on a highway shall be equipped with a system of lights which may include retroreflective reflectors, identification, clearance and side marker lights in conformance with regulations of the department.
(e) Equipment exempted by regulation.--Antique motor vehicles, animal-drawn vehicles, implements of husbandry, commercial implements of husbandry and special mobile equipment, if operated exclusively between the hours of sunrise and sunset and not during periods of reduced visibility or insufficient illumination, may be exempted from certain lighting equipment requirements of this part by regulations of the department.