Caster Mod for pre 73

[66 C10 383]

I'm looking at having the lower a-arm shafts drilled to do the Caster Mod on my 66 C10. Here's the write-up that originally got this started but his was the 73 up bushing style.

http://67-72chevytrucks.com/vboard/s...d.php?t=501241

For us guys with the older style a-arms, what are you having them drilled at? I've read anywhere from 3/8" to 1". I just want I nice driver, nothing excessive. Mainly interstate driving in the 70mph range.

I'd like some input on how much you moved them and, if you've had it aligned, how much did you gain. Did you have any spring or shock alignment issues? I'll do the FrizzleFry shock mod so that won't be much of an issue.