I used a brass screen type filter (for the early model TH350) and the regular hygard cut with a couple quarts of Dex 3 so i can see it on the dipstick. The converter I ordered was a little sloppier and this seemed to tighten it up a couple hundred RPM.
I don't think this old GM stuff is picky...
I've got stainless Hooker street stock headers on mine. Can't say I'd recommend it but they can be made to work dimpling a tube on each side to clear the control arm and minor trimming at the firewall. If you've got tubular lower control arms it would be a piece of cake...