What's the differences in control arms?

[springer1981]

I know there are 2 different sets of control arms, early and later style. Help me understand if I have this right.

Lower control arms
LF and RR are the same
RF and LR are the same
Is the only difference in the early vs late the ball joint hole size?
Am I correct to understand that you can simply drill out the hole size and use the later ball joint?

Upper control arms
All 4 are specific to their location, example right front only fits right front.
Only difference is hole size early vs late?
Same, drill it out and use late ball joint?

Thanks

 

[TOBASH]

New ones have a plate added to distribute forces around the interface between the ball joint and the perch on the control arm.

I drilled my holes out and painted them to prevent rust when I replaced the ball joints. I did not add the plate but others do. A friend drove 200k miles on his old style control arms and ball joints (He drives an H1). He off-roads weekly and seems to be OK without the plate. Others like the plate.

 

[Retiredwarhorses]

I know there are 2 different sets of control arms, early and later style. Help me understand if I have this right.

Lower control arms
LF and RR are the same
RF and LR are the same
Is the only difference in the early vs late the ball joint hole size?
Am I correct to understand that you can simply drill out the hole size and use the later ball joint?

Upper control arms
All 4 are specific to their location, example right front only fits right front.
Only difference is hole size early vs late?
Same, drill it out and use late ball joint?

Thanks

You don’t want to drill out 3/8 lowers to 7/16 as it leaves very little meat left on the bone around the larger hole.
The newer style Arms also use a newer style bushing that’s not serrated.
Newer style lowers allow for variable rate springs
Newer style can be identified by the 2 small holes underneath as opposed to the single large hole.
All newer uppers have the reinforcement ring welded in and are 3/8 Upper BJ’s.