Got a 53 SportCoupe w/tweaked 350 smallblock. I know a couple ole hotrodders that owned or knew 53 SportCoupes that had v8's installed. These guy's tell me that these 53's would torque os bad comming off the line that it would chip paint off the front fenders. I love my old car but I also love the HP and oversized cam .Preparing to take her off frame for floor pans. I am considering rolling the tophat out and sliding in something newer, like 70's 80's chevy designed for a v8 Any input for or against welcome. Also would be grateful for info on what would be a good frame to start with?

You will probably have better success getting the desired information on Chevytalk or another site. Most of the expertise on this site is non-modified vehicles. There are some hot rodders both modern and from their early years so you might get lucky and have one of them see this post and respond.

Yes, you would find more info for "modified" Chevys at Chevy Talk or HAMB.

I had a 54 with a mild built 350 back in the mid 80's and early 90's and never had a frame problem, my cousin still has the car. The 41 that I have now has A 383 tuned port with a mild cam and over 25000 miles with no problems.
How much hp, and how are you going to use the car, ie drag racing or street. There are several streetrod vendors that build new frames for that vintage Chevy. I do know of some that have used 78 to 88 Gm A body, Monte Carlo Malibu frames under 49 to 54 Chevys, but I think they have to be lengthened to work.