hd 5 speed swap. need some advice

[292farmer]

ok i have a 1972 GMC C25 w/ 292 SM 465 and a 5.13 equipped dana 60, i was thinking a t5 but it would be woefully in adequate. i am thinking of swapping a NP540go into my truck and/or maybe a spicer aux. trans(5831 series). i used the search feature for about 3hrs but didn't find much so felt safe posting my question.
i found this website of a guys who done it.(the 540)
http://www.bethsbackyard.com/NP540GL...escription.htm
does it explain everything right? seems he just bolted it in no prob what other bellhousing will work? i was thinking of looking for a c40 up series 292 bellhousing like in the older trucks 60-66era. would that require a big truck clutch or my stock 11in.
also what other types and models of trucks came with the spicer aux. trans? im looking for others that have done this and also any tips or ideas you all have. and maybe some threads about this that i've missed?
thanks everyone.

[padresag]

what do want an aux for
the np540go has a granny gear
ron

[292farmer]

quite a few aux. have either a .82 0r .73 OD and the 3 ranges would help fill the gaps between gears. when towing on slopes. their are two models that are only underdrives, and i dont need those lol.
spicer 5831b,c,d are .85OD 5831, a,e .73OD middle is 1:1 and low ranges from 2.35 to 1.27:1 5831f, g are the underdrives.
i have between 8 to 12 driveshafts at my dads so the aux, set up as a divorced unit would be the easiest swap for me.(yet its the only one i dont have yet. ive got a 540(2 if u count one in my c60 in my sig) plus ive got t34 with .82OD but feel that would be hardest to swap in. still researching it though.
if did math right
with 540 or t34 with 5th-.82od w/5.13s w/235/85r16 give me @2000rpms =45mph about 4.206final drive ratio
with 5th-.82od and aux .85od @ 2000rpms w/5.13 w/235/85r16 =53mph about 3.57 final drive ratio
with 5th-.82od and aux. .73 @ 2000rpms w/5.13s w/235/85r16=61mph about 3.07 final drive ratio
id only use double od when empty, however may be able to tow a decent load with only one od

[raycow]

That is a very well documented write-up. From the pics, the writer's 540GL appears to have a normal Chevy bolt pattern. I think the only reason he had to change bellhousings was to get the right size center hole because he was replacing an SM465. 3815891 is the common 4-11/16" bell used 63-67. There is nothing weird about it and they aren't particularly hard to find.

The bearing retainer size depends on the model year, and I would expect any 68 or later transmission to have the larger 5-1/8" retainer. Just measure the retainer on your 540 and select the bellhousing accordingly.

Ray

[292farmer]

now am i correct in thinking that the spacer ring many talk about in their threads, is a ring to adapt say the 4-11/16in to fit the larger 5-1/8in? maybe a route i can consider.

i believe the trans is a 71-72, so it should theoretically be 5-1/8in and therefore should bolt up to my current housing, with some minor modification. am i correct in that line of thought.

[292farmer]

found this on a jeep site, will their bellhousing and clutch kit and adapter plate they use work on my 292? i thought maybe the 292 rear motor to bellhousing was different from sbc, but maybe i remembered wrong. figured that maybe if that bellhousing will work too, opens up my parts availability options and transmission options if my 540 isnt in best shape.
http://www.jpmagazine.com/techarticl...ion/index.html

[raycow]

Originally Posted by 292farmer

now am i correct in thinking that the spacer ring many talk about in their threads, is a ring to adapt say the 4-11/16in to fit the larger 5-1/8in? maybe a route i can consider.

i believe the trans is a 71-72, so it should theoretically be 5-1/8in and therefore should bolt up to my current housing, with some minor modification. am i correct in that line of thought.

Yes, the ring looks like this and would be needed if you want to bolt any 4-11/16" transmission to a 68 or later truck bellhousing. A similar ring is also available from Novak and Advance Adapters. My personal preference would be to shrink it onto the transmission rather than press it into the bellhousing. Less chance of knocking it loose that way.
http://dennymac.com/mod.php?mod=user...103&page_id=54

Your 71-72 transmission should work without the ring. I am not sure what modification you are asking about, other than maybe the shifter hole and of course the driveshaft.

Ray

[Jacfourteen]

Sounds like a cool swap! I saw an old dodge on youtube with a 2 stroke diesel and twin sticks and it looked like a blast to drive. you would have a total of 15 forward and 3 reverse gears, tell me that wouldn't be cool .

[292farmer]

its real cool especially when u show off too your buddies they think its like voodoo my dads mack B60 has a 5spd +3spd aux with 2 speed rear end 30forward and 6 back!! plus my c60 when i had it on the road was a 5 spd plus 2speed rear. and when u really want to get them shift with out the clutch!!!