LS1 bolt pattern
 

does the LS1 and small block chevy have the same bolt pattern for the bellhousing.wanna put a 4L80E from 6.0 truck behind my 436 sbc chevy.

Not only a different bolt pattern, but a different input shaft on manual trannys.

yeah i figured that just gonna have to stick with my 400turbo and get manual valve body for it.

From what I've read on LS forums, the bolt pattern on the LS motors is the same as the gen 1 sbc. You can easily mate a LS motor to a gen 1 sbc using a spacer on the crank to flywheel. The reverse (4L series trans to gen 1 sbc) could be a problem as the torque converter on a 4L60 or 4L80 would probably be too close to the gen 1 crankshaft. I don't know if there's a spacer available to get that dimension right. If you're interested LS1tech.com is a great source.

thx i appereciate just trying to see what my options are for an overdrive tranny that will survive thru the abuse i will give it with my 436,i have a 700r4 but not sure if it would last very long.

The LS series trans bellhousings have one less bolt. The torque converter is deeper, so from what I've read you might need to space the trans bellhousing mount if you get the later post 1995 4L80E.
I'm still researching this too, as I'd like the extra gear to get a little more gas mileage and lower rpm's at cruising speed.

yeah me too,i just dont want my engine to have to run so hard on the freeway,val if u go to nastyz and type 4l80e theres a few good articles about it,someone is also making the torque converter for the swap so no spacer is neded.i can get a 4l80 cheap here found one for 300 dollars from chevy truck with only 65,000 miles on it.im gonna go with the manual valvebody.

val just found a 4l80e out of 96 suburban thats originally mounted to a 350 sbc,didnt know they used the tranny on the sbc.that will save me lots of hassle and the tranny is only 400 bucks cant beat that.i have over 1,000 dollars in my 400 turbo wish i would have know this before.

They're definitely strong, but not cheap, even if you get one for $300. The manual valve bodies seem to go around $500-$600. I'd want manual too, as both my automatics are manual now. I still haven't decided the 4L80 would be my choice. I may go the 700R4 just becasue it's less money, and has a lower 1st gear.

The LS motors have an extra bolt at the top of the bell housing that the sbc doesn't have. From research it isn't needed. There have been many 4L60s and 80s swapped into older cars so I'm sure there's spacers or custom torque converters available. I'm debating on the same thing. I have 3.73s and would like a good OD trans for highway driving.