73-87 GM a-frames (control arms)on pre 73 2WD trucks
 

Who has taken some accurate track mesurements before and after this retrofit to determine if the track actually increases (which is what I've seen written elsewhere on this forum). What is the measured increase? I don't want to use the wrong modular dropped spindels (there are two versions one for each generation of a-frames) and lose any of the advantage of narrowing the track by changing to the newer GM A-frames (control arms). What about spindle arm/tie rod end interferance with the inside of an aftermarket 8 inch "corvette" style rally wheel (5 on 5) with 4.5 inches of backspacing? I'll need 1/8th inch of clearance between the wheel and the head of the tie rod. I know 5 inches of backspacing with the same style wheel won't work with the stock GM a-frames on my 72 2WD blazer. I ruined one tie rod by "massaging" it with a die grinder to create clearance, bad idea! Advise thanks, norv.

Re: 73-87 GM a-frames (control arms)on pre 73 2WD trucks
 

No 'official' measuring, but I've stood the pre-73 & post-73 lower a-arms side by side to compare. There was no notable difference.

The track width increase is associated w/the drum to disc spindle swap. The spindles are physically different dimensions for the hub area (the disc being the wider unit).

Re: 73-87 GM a-frames (control arms)on pre 73 2WD trucks
 

I agree with SCOTI.
You also increase the track width when you use shorter coil springs.
(the lower a-arms are flatter,... thus wider, by a small amount)
A 15" wheel with 4.5" backspace will definitely cause issues with the lower a-arm in the balljoint area,... and poosible the tie rod.
Anything over 3.5" backspace on a 15" wheel will cause interference.