Radiator NSN is 2930-01-132-0978 and the part number on mine is 816A.
http://www.govliquidation.com/auction/haystack?nsn=2930011320978
Until I see something that convinces me to change I'm going with regular antifreeze + SCA. I think it's important to check with test strips. They are pretty cheap and make it easy to keep the additive at the correct level.
I think the radiator cores are the same on the HEMTT, PLS, and MK48 even though they have different NSN and part numbers. I have a couple MK48 radiator cores that I've taken measurements on & they match the overall dimensions on the core of a PLS radiator I have. The bolt patterns of the tanks look the same, but I haven't compared them close enough to say it is an exact match. If someone has mapped out the dimensions & bolt pattern on a HEMTT core, I'll do the same on the MK48 core to see if they are interchangeable.
HEMTT Figure 58 page 172/1469 TM 9-2320-279-24P-1
-------- NSN ------------- CAGE ---- Part#
2930-01-132-0978 ---- 45152 ---- 1349840 complete radiator assy
2930-01-133-9954 ---- 45152 ---- 2AE954 core
.
PLS Figure 48 page 121/813 TM-9-2320-364-24P-1
-------- NSN ------------- CAGE ---- Part#
2930-01-373-5991 ---- 45152 ---- 1882370 complete radiator assy
2930-01-357-5722 ---- 73540 ---- 2100-50865 core
.
MK48 Figure 54 page 172/1605 TM-08780B-24P
-------- NSN ------------- CAGE ---- Part#
2930-01-181-6743 ---- 45152 ---- 2190280 complete radiator assy
2930-01-207-0633 ---- 45152 ---- 2CP301 core