I really like the 12 bolt, but to get one to fit a gen 2, they're rare. My 1970 Formula has one. I can get a truck 12 bolt for $75. My plan was to order replacement axles for the '70 and then take the difference in the lengths of the truck axles and that would be how much to cut out of the housing. I'd measure the spacing of the axle flanges from the housing as well. Does this sound feasable? Most truck 12 bolts are 6 lug anyway. I know someome will ask "why not just measure the '70?" Its still in storage at my parents 2000 miles away.

 

Hmm. I would cut the housing the same width as the 10bolt your replacing. Perches the same way. Pinion angle too. Then when its ready for axles call and give them the measurements and they will send you exactly what you need. The price isn't really gonna be that much different. Do you have a jig to weld the flanges back on concentric? Might wanna farm it out.

 

I think your idea of going with a truck axle is great! I too would have it cut exactly the same width as a stock 10 bolt and use the stock axles for a 1970 12 bolt. That way if you or anyone else ever needs axles again it wont need to be some special order later.
I've had a local builder do most work on axle housings. It's too important and too dangerous if I screw up a weld and it fails. Dutchman's Axles is less than a mile from me and they do fantastic work for reasonable prices.
You can weld axle shafts and have them hold up wonderfully, but it takes a very good welder and a lathe to properly cut and dowell them to be straight and strong. Same with housings. They need to be cut off properly to be able to press them into the third member before welding. Properly done they'll be stronger than factory housings.

 

I've seen the jigs, but can't find one yet for a 12 bolt. They had a good episode on Extreme 4x4 that showed how they went about narrowing one. It's pretty dang expensive to have done. I was going to tack it pretty dang good then have it tig'ed. I used to have access to a machine shop, but moving messed my car plans up. i think i'll put it off until I can go home and measure it exact. I can find '69 camaro and Nova 12 bolts in the 1200-$1500 range. Narrowing it was ~$1100, I'll have to price this out when done. Alot of the point is a project/learning for me. I've learned all kinds of interesting stuff this way.

 

I have a buddy with a jig for a 9' ford. It came in damn handy when I warped mine welding on a brace. It seems like you could almost go aftermarket for 1500 bucks. Makes me cring knowing I sold one for 75$ ten years ago.

 

12 bolts cost more to narrow than a 9" Ford because of the third member. On a 9" it can just be pulled as a unit, which keeps everything from being torn out and reassembled. The 12 bolt needs allt he parts removed prior to cutting and welding or risk heating things up too much.
Have you considered finding a 9" Ford from a Ford truck and putting that under your car?