Reviving this post because I'm in the same boat; have a 1986 LT9 (M) in my 1-TON GMC 2wd pickup that needs to be re-engined.
Looking at GM crates at JEGS and guy says '86 is a transition year and I need to be double sure I order the right engine--- either 2 piece or one piece rear main CS seal.
Short of pulling the engine right now, I thought maybe somebody may know if there are some external clues to help determine 2 piece from 1 piece blocks.
Understood; flex-plate and bolt patterns differ as well as oil pan.
Did GM block ID Wild-Goose-Chase and only thing I came up with was my FRONT PASS-SIDE block # V0702UPY, which is supposedly the date of the block manufacture. Running the UPY part of the code I get:
UPY '86 350 Truck 160hp LT-9 4bbl C/20C30 - that's me!
AND
UPY '90 350 Truck 200hp L-05 TBI ALL MODELS 4x4
Question; any guesses on how reliable this info IS and would it be safe to conclude that these are ONE PIECE RR main CS seal blocks?
Also, I believe that '90's trucks ALL went to TBI/Vortec induction and hence; my stock 4bbl intake will not fit this setup. Has anyone else been caught in this 1986 dilemma? Results?
FWIW: Looking to keep this truck bone-stock 'cause I have to please the Calif Smog Nazi's and anything other than stock will cause miscreants to suffer a thousand cuts.
Also, being as today is Sunday I will give my GM dealer a call tomorrow but experience shows that at times they are not so helpful unless you act like a serious parts buyer... OK, how 'bout an intake manifold gasket for your trouble sir?
