I ended up rebuilding the bottom end as a forged 383 in addition to the mods above and rebuilding the T56, so things took a while longer than anticipated. I also got a mail order tune from Moe Bailey...

45 mph lets you get into OD if the shift tables command it, which is just under 1400 rpm when locked up. If the "cam surges" smooth out around 60 (1850 rpm) then it could be a cam surge since your...

I found this forum through Eehack - looks like a great resource!

I've done some tuning in the past with Eehack:
-AC install
-Gearing change
-Higher stall torque converter
-Shift points...