Caps are welding good metal over old rotten metal. Not a good combo IMO. I've done a couple set of partial rail replacement's in B-Bodies (mid axle hump back), and would recommend you just cut the old garbage out and replace with new.
As far as the complexity of the repair, it's not terribly...
I'm in the middle of restoring a 1971 Dart from California. It's a factory slant six car, with factory EV2 Paint (Hemi Orange). I scratch my head too.....High impact color, low impact motor? Who knows, lotta drugs floating around back then
http://www.megapartsusa.com/proddetail.asp?prod=145-ASR101
That's funny....I created and posted that picture with the red arrows on FBBO like 4 years ago....looking for the same parts for my RR.
You'd be correct. 64-70 had the ball detent style (which this one is). 71-Up would have the interlock (raised casting line between detents)
1968 and on tranny's would have the raised machined pad for vehicle serial# and production date.
Any idea if this guy is over at FBBO under a different alias possibly? I can imagine he'll be looking for more victims across other Mopar boards, especially since he's banned here now.