318 Street/Strip build?

I like to measure and buy steel square tubing or channel, cut accordingly and weld in. I personally like “everything welded to everything else” construction where possible, the more you can tie in together, the stiffer it gets. It’s not nearly as critical in an a-body as in cars that weren’t designed for a V8 to start with, though, but being that your into it anyway... A flux core wire welder is a good investment, if you don't already have one. I have one of the $89 120 volt Chinacago Electric units from Harbor Freight and it works well enough but it is a little sloppy because the wire feeder is not robust enough to be smooth, the 230 volt unit may be better because it has gas feed. CO2 and Argon blend work well with flux-core wire when welding overhead.