inside coil air bags?

[matts70chevy]

I have a 1970 1/2 ton pickup that we are in the middle of installing front disc brakes from a 72. I was wondering if there is an air bag type of device that fits inside the coil spring to stiffen the ride. I'm looking to replace the 350 with a big block and I thought this might be a good way to support the extra weight. Does something like this exist? If so, what do you think about going this route? Thanks.