New PowerTrain Project

[Branch68]

Hi, I'm new to forum, but have been a frequent lurker for about a year. Last summer, I bought a 68’ swb stepside in very good shape. I have already been enjoying it and have completed a few good projects. However, it is going to get ‘serious’ soon and this will be more ambitious than many of my car projects. So, it’s a good time to get some other folks thoughts before I start spending money. I figure a thread to document and ask questions along the way might be a good thing. Here it goes!

Where I started

The truck was in pretty good shape when I got it. I’m guessing it was restored something like 10-15 years ago and two owners ago. It doesn’t appear to have been driven much, and looks like most of that time was spent covered. The paints not perfect, but she’s rust free. The most recent owner converted it to a manual Muncie 4 speed and gave the existing goodwrench engine the “quest” treatment. He also lowered it. I *think* it is lowered 4 inches all around. with spindles/springs in the front and blocks/springs in the back.

What I’ve already done

Since I’ve had it, I’ve fixed a lot of the little things (oil leaks, speedo, power-steering). The one big project I completed was to convert it to fuel injection. Here, I went the road less travelled. I built a megasquirt MS2 from a “build your own” kit. I soldered the board, built my own harness and fuse panel, sourced the sensors, and a NOS holley 950 cfm tbi unit on. Lots of learning/time, but I’m pretty happy with the result. I also now have the headroom for a much larger engine.

Where I would like to go

My lovely wife gave me a TKO600 kit from American powertrain as an anniversary present. When I install this, I’m thinking I’ll do a power-train upgrade front to back. My intent is to build it up to be a better street truck, with north of 500 hp. It doesn’t need to be full pro-turing or pro-street. Just a good fun ride that jumps when you stomp it and won’t scare you to death in a corner. I’m thinking I’ll build a SBC 400 that redlines somewhere around 6-6500rpm. I plan to keep a stock’ish suspension setup perhaps with simple mods to improve suspension geometry/handling/ride. It is also already lower in the front than I’d like, so I may replace the front drop springs to remove the rake.

First Question/Purchase

So, I’m thinking the first big thing I need to decide on is the rear-end. Should I upgrade the existing truck 12 bolt or upgrade to a ford 9”? I’ve done some looking at parts/prices. It looks like I could easily spend $1000-1500 for axles, ring, and a trutrac for the existing truck 12 bolt. If were to go with a ford 9, it looks like it is at least $2500 for a drop in by Strange. The first gear of the TKO600 is 2.87, and I doubt I would have either 4.11s or 3.73s to cruise at around 70 mph@2000rpm. So I’d have 6400-7000 ft-lbs on the axles.
Is the ford 9 worth the extra cash for my plans? I hear a lot of folks say the 12 bolt truck rearend is no good, but I haven’t seen any first-hand accounts of breakage much less any real data on power-level. Is there better places/prices to get a non-junk-yard ford 9?