DO like that torque arm setup w/ bags.
Clipping is a lot of effort and can go bad if not done properly. Not that I dont have the ability to do such, but like you mentioned, the full frame becomes no too far off.
I intend to use bags / air ride system being I am going for the grand tourer style build. These are classy cars and should handle and look as such. Had the '56 out today after the brake job and I came back w/ a big smile.
While its no BMW in the twisties, it did fairly well considering 57 year old technology and 87 turn lock to lock steering. Actually much older technology. I think '58 was the first year for ball joints.
Anyhow, your suspension design will be greatly impacted on the overall type of focus you want to build your car. Personally, I prefer a three link, but the ease and egress of a 4tri-4 link may be the answer. After more R&D, I will have the answer for my build. Hopefully you will will as well. I do know that the kink pins will not be in the future.