Originally Posted by pasbonsimon

question, with the factory LS1 flexplate and convertor for LS1 to TH350, do you still need a spacer if the convertor is made for the LS1?

Originally Posted by demonpixel

This info is AWESOME.

Quick question:
If you are using a stock flexplate (mine is a 98), do you need to use the longer bolts (pn 12563533) with the Hughes spacer (pn 3795), or do you only use the longer bolts when using the gm stock 6.0 crankshaft spacer (pn 12563532)?

In other words, can you use the stock bolts with the Hughes spacer and a stock flexplate?

Thanks again Jay!

Originally Posted by 71 chevy

so here is my question - as Im a bit confused here

a stock 5.3 engine with its stock flexplate- do I need anykind of spacer to get it to bolt on to a th350?

I can understand the need to have the spacer between the crank and a flat flexplate from a 6.0 but I cant understand the need for a spacer AFTER a dished type flexplate.

Originally Posted by jay_lt4

someone make this a sticky

here are the facts about fitting an old style trans to the gen3 engines

1. the gm gen1,2 trans will bolt to the gen3 engines but you only use 5 bolts, the gen 3 engines do not use the middle bellhousing bolt on the pass side( no big deal)

2. you do not need a special flexplate, the curved 4.8,5.3,LS1- just need the t/c bolt holes ovaled out a bit and the 5.3 flex plates have a set of holes that match the small gm t/c bolt pattern perfect

- the 6.0 flat flex plate has the same t/c holes as the large gm pattern(th400 and most aftermarket th350 converters that have a dual t/c bolt pattern on them)

3. you need to use a crankshaft spacer when using a gen1,2 trans and converter there are 2 types:

- hughes gen3 crankshaft spacer part # hup-3795 $44 from summit/jegs, this spacer must be used with the curved 4.8,5.3,LS1 flexplates

- gm stock 6.0 crankshaft spacer 12563532 and longer bolts 12563533, this spacer can be used with either the flat or curved flexplate ( if using the curved style flexplate the flexplate goes on the crank first then the spacer goes on then the bolts, if using the flat 6.0 flexplate the spacer goes on the crankshaft first then the flexplate then the bolts)

i have used both style spacers, on several 5.3,LS1, 6.0 swaps and have not had any problems with either set up

Originally Posted by DanZ28

You also have the option to buy an LS1 converter built for a TH350/400 and not use any spacers at all. But it's good to see all the info in one place instead or reading through 10 pages of the sticky/FAQ above, so good write up .

Dan