[T/A addict]

I purchased 2 400 motors a while back (from different people) that were supposedly "good running recent rebuilds")..... Well I'm having nothing but more and more issues with them as time has gone on and getting very very frustrated so I'm thinking it may well be time to quit buying used and build my own "first - so expect some rookie questions" motor. So here I am to ask the experts some good build recipes.

The car - 69 Firebird - will be mainly just a strong street car with maybe an occasional race/strip pass. Has a 12 bolt/4.10 so an OD trans will surely be a must..4L80E maybe. Not wanting to spend a fortune just something moderate, I do have some items already for the build and ideas..... Stroker kit

I have a set of 6X-4s that have been ported/polished and has all pos valve seals with 211/177 SS valves, guides/springs, elongated push rod holes all casting materials cleaned up, spring pressure should be about 110 to 120 seat and about 160 open, 90cc chambers- estimate will have to measure to make sure.
I'm set on using this set of heads.

I have one of the 400s in the car and one on the stand.... I've also been considering buying a 455 block. Would it be better to go the 400 or 455?
If I strip the 400 and use it what do I need the machine shop to do? I think a .035 bore for the stroker kit would be expected at least?

I'm thinking a roller cam like this one - Hyd Roller 227/235@.050 .525/.530 109LSA 4/7 Swap Rattler
: https://pontiacspeedshop.com/hyd-rol...-swap-rattler/

I do also have all new Dual Sync distributor, Sniper Hyperspark ignition box, Hyperspark coil so thinking I will go with a Holley Sniper.