You don't need to have 400hp and one ton junk to have a reliable Jeep.
Wow, you don't say!? If he's gonna go through the trouble of changing to a Chevy Motor, changing the mounts, fabing a cross member etc... Then why not bolt up the rest of the goodies... You know as well as I do that Countless numbers of 350's had a wide variety of HD trannies, (Auto/Manual)... No worries about bolt patterns etc... Here, I can walk into a yard Grab a Chevy 350, Granny tranny... or an TH350/Th400... Finding an NP205 is fun but that's what Ebay is for
I would swap in a Jeep 304 or GM 305 in a heartbeat. Both can be very reliable and make respectable power without dumping too much cash into them.
The 304 is JUNK... You might as-well drop in the 258 with minor bolt-ons (Which will equal or better the 304)... The 304 is a dog no-matter how you look at it... Even with an intake/carb/headers... But you'll be pushing over $600 for these simple mods... The 305 isn't much better either.. Unless you get the HO 305... Pretty much all 5.0's are Junk... and I hate to say this But the only 5.0 that I'd drop in my Jeep would be a FORD 302... (I can't believe I said it). Complete roller set-up, fuel injection tons of after market junk (Still kinda pricey.. for Ford parts
The key here is a reliable Jeep, that will get you around town, get up and back down the trail, and get you home... time and time again. If you go tossing in huge power, you will eventually start breaking other components, run into cooling issues, and longevity issues. Keep it simple & reliable.
I can't agree with you more... I prefer to build my rig(s) with 1 ton stuff... For long term reliability... I know this stuff will handle the loads/stresses that I'll toss at it... Now, as for my motor... She's definitely Over Built for Crawling... She's been worked and detailed covering all aspects... I know this motor will last for a while... Now, If i go out mudding every weekend and hold her at 7000 then yeah she'll end-up beat...
The GM drivetrain is long. You will need to address driveshaft lengths, and if your lifted, you'll likely end up having to CV the rear shaft. This in itself can be expensive.
is only 10.8"
long... The T18
Long... The NP465
long.. The SM420
long.. The TH400
long... The TH350
Another option would be to rebuild your 258 and look for a T176 four speed. If you've had your 258 on the trail, running well, you know it's a workhorse and can make your Jeep do things that will have the V8 guys scratching their heads. I love my 258, with the HEI and MC2100, it's never left me stranded and always got me home.
I had a 258... It was great... I also had a 304.. I thought that it was Junk... (Good power but the difference between the 258 and 304 was minimal)... I had a 360 and loved it... Now I have a sickly built 360 and I'm sure I'll enjoy it even more... (I'll probably drop it in an AMX or Javelin).
My best advice is... Find what you want to do with your Jeep... save up for all of the parts etc... and then build the Jeep stronger than what will be needed... Build once and never look back... Build it weak, and you'll be the guy holding everybody up on the trail... or you'll be off to the side in the pitch black working on the rig. (Hoping that somebody is soon to come along... asking yourself. "Where the hell is the trail rig"