I need some help here. I am running a solid axle 4Runner with a M112 mounted ontop a 1UZ. I don't wheel the truck hardly ever, but certainly want to be able to if I want to. It is mainly a just a street driven 4runner. That being said, I will be engaging the 4wheel drive (high) when playing around, to keep the front 33" tires from spinning. I have spared no expense on this build, and don't want to be replacing axles anytime soon. Should I get Chromoly axles shafts and birfields for the times I want to enter 4wheel high and not worry about the HP breaking anything up there? or shoud I get chromoly Axles shafts but keep OEM birfields as to avoid the birfield to wear out due to the softer chromoly, which I won't need because I wouldnt be running a risk of slamming it on rocks. Or would you suggest another combination? I need advice.

Most people don't have any issues with factory axles and birfs, as long as they aren't throttle jockeys.  But with that combo you have, it wouldn't hurt to with chromo or Bobby Longs.  And be done with it.  I plan on going with stock birfs until I can afford Longs later. 

obviously upgrading to longs is the best thing he can do from a strength standpoint, i think he already knows that.  What seems to be a more concerning issue here is the fact that he wants to be able to run in 4wd high range from time to time, without wearing out a full chro-mo set of longs.

Travolous- you mentioned maybe running cro-mo inner shafts with stock birfs.  I dont think that would really benefit you in any way.  The inner axle is much stronger than the birf already, so putting a stock birf on a chro-mo inner is not going to gain anything, because probly 95% of the time the stock birf is going to break before the stock inner shaft anyways.
I think you have two options here - run the stock stuff for a while and see if you have any problems with it
                                                 - or upgrade to longfields and only run the vehicle in 4wd high range when you absolutely need it so you dont wear out the longfields prematurely.  Then when you do get the 4runner in low range out in some more difficult rocks and things, you wont have to worry about breakage since you are already upgraded to longs.

Another thing I would do is talk to the folks at Longfield to see if running them in 4wd high range every once and a while is going to damage them, or if its not really a big deal.  I know that Bobby has passed on, but i'm sure there is someone there that can make a recommendation for you and give you more info on how much 4wd high range driving is too much for the longfields.

Just called Longfield, and they believe that the 27 spline chromoly setup will be perfect for what I need. It should handle the high horsepower application just fine. Curious, what are the opinions of the longfield vs. the other guys, like the MC set that they sell? Why doesn't anybody ever talk about those lol ?

Longfields have the best warranty!!   

From cruising the forums, alot of people run TG stuff, but trying to get them to warranty it is a different story.  I hear alot of shady reasons of why they won't warranty a lifetime warrantied product. 

If and when I upgrade axles, I plan on giving Marlin a shot first, then if I ever have any troubles I'll go to Longfield.  I don't plan on doing any hardcore stuff.  Mostly just trail riding, old Fire Breaks, and doing some things that a IFS has trouble with.

Sorry to say, he hasn't been on Marlin for a couple years.  Ever since he started his fab company.  http://www.c4fabrication.com/

Kinda miss him around here, he had some mad skills!