[EagleScreech]

Jason, I sent you a pm regarding the files! Thanks a million.

I think the differences are really minor- the shocks on 63-66 frames mount forward off the axle tube up to formed mounts on either side of the frame. The 60-62 frames have shock studs off the lift blocks up to the parking brake crossmember.
Also, I believe the horseshoe motor mounts were phased out in 63 and GM went to the good ole 3 bolt side mounts.

Side note- My 283 has a road draft tube rather than a PCV valve and the single ball stud boss for the old style linkage. My bellhousing is also factory drilled and tapped on the passenger side for a clutch slave.

All of that info jumbled together makes me 79.8% sure it's a 62. Anyone with more knowledge than me please jump in with some school!