I was told that the S-10 frame only really works for the big fendered 40's cars ect. As far as an original model A frame it would have to be in good shape and straight to bother boxing it. I was planning on a scratch build for a model A and was going to buy a modern frame. Depending on who I bought it from it would have been $ 8000 to $ 11,000 by the time I got it into Canada and paid the duty and shipping. I ended up buying a 28 coupe already mostly done with a TCI frame already under it.
I like Dave's idea of the deuce frame as my car has a 4 " recessed firewall which makes distributer removal near impossible. My frame is an exact replica of the original model A frame however if I was to order one I would get the one that is pinched in the back end.