Ya I ran an SM420 behind my 6.0 in a 67' Chevy K10, had the Rockwell T221 t-case which wasn't the greatest but worked well. To use one on a Gen III/IV motor though you would have to either fab up a bracket to house a slave cylinder or clutch linkage if your using a clutch fork or switch to a hydraulic throwout bearing since the LSx blocks don't have a place for the pivot ball on the side of the block, as well as needing a longer/larger pilot bearing.The TH400 is short but so is a 700R4 and it can be built fairly stout as well and have a better 1st gear and weigh less, just my .02 but either is a good choice. One of the members on the Planet did a 700R4/Dana 300 swap in his SAS'd Rodeo. I'm gonna go with the MUA5 because it'll work well for my needs and look completely stock inside and I can bolt the tranny up to the trans crossmember and then position the new motor mounts accordingly (as long as oil pan etc clears). Too bad they never made a T56 in 4wd, I was going to use one in my 67' with a divorced NP205 but ended up selling the truck. I did an LS1/T56 conversion in an 87' Iroc that was originally a 305/700R4, now that car was fun! Even built my own long tubes for it. I didn't know the 3.5 had the cross bolts as well, that's pretty neat on the 3.5, seems like such a nice platform to have so many issues on the bottom end. Those guys over in Australia have it nailed down though! If I go 5.3 in this one I think I'm gonna go with an LM4 or L33, save a little weight off the front end and just like the iron blocks, they can be bored out. I haven't done it but from what I have read on the aluminum 5.3's is that the outside diameter of the sleeves are the same as an LS1's, just thicker walled to bring the bore size down, so you "should" be able to bore out to a 3.9 bore and have an assortment of pistons available instead of just Wiseco's.
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