flex plate woes
flex plate woes my 99 LS1 is going in my nova, I bought the crank spacer and it fits right up, but the Flex plate does not. the bolt holes don't line up on the flexplate to the spacer/crank. 
I ordered a stock replacement for a 99 TA A4 flex plate. went back to my parts guy and he says the part number of the plate I have is what is supposed to go on my engine but they don't match up. is there something I'm missing here?
I ordered a stock replacement for a 99 TA A4 flex plate. went back to my parts guy and he says the part number of the plate I have is what is supposed to go on my engine but they don't match up. is there something I'm missing here? 
There are two style flexplates. One style is an offset design for the 4l60e transmissions. The other style is the flat flexplate for 4l80e transmissions.
When using a TH400, you need to use the flat, 4l80e flexplate. These flat flexplates come with the appropriate spacer from GM. The whole set up is about $60 new.
When using a TH400, you need to use the flat, 4l80e flexplate. These flat flexplates come with the appropriate spacer from GM. The whole set up is about $60 new.
GM part # 12621399 Flywheel & spacer assy (used to adapt LSX motors to old school automatic transmission)
This information was taken from my swap parts list. You can see everything I have used for my swap at:
https://ls1tech.com/forums/14092457-post4.html
Two extra bits of information. You will still likely have to slot the torque converter bolt holes about 1/8th of an inch. And, if you are going to be making big horsepower and drag racing, you would be better off running an SFI approved racing flexplate from a company like Hughes. Hughes makes an SFI flexplate and adapter for LS motors using older transmissions. Theirs is considerably more expensive, but I don't remember how much.
This information was taken from my swap parts list. You can see everything I have used for my swap at:
https://ls1tech.com/forums/14092457-post4.html
Two extra bits of information. You will still likely have to slot the torque converter bolt holes about 1/8th of an inch. And, if you are going to be making big horsepower and drag racing, you would be better off running an SFI approved racing flexplate from a company like Hughes. Hughes makes an SFI flexplate and adapter for LS motors using older transmissions. Theirs is considerably more expensive, but I don't remember how much.
