If you're worried about the rigidity of the chassis when removing the spare tire well, just weld in a cover with an access hatch where your sump is, in case you need to service it. But I really wouldn't be worried about it, there are a lot of people removing their spare tire well for fuel cells, and I've never read or heard of any issues.
Losing the space is a personal question. My last sports car was a Datsun Roadster. There was no spare tire well, so if you carried the spare, it took up over half the space in the trunk. I got over that quick and just carried a AAA card instead.
I'll be using the stock Camaro plastic tank, which will allow me to route the fuel filler to the original location, and not get too fancy with dual exhaust routing. But I think you'll be running a single exhaust with the CX kit, so that is less of a concern.
Also, I don't know much about racing sanctioning bodies, but if you are planning on tracking the car, you may want to confirm what will be allowed. The "fuel cells" that that they sell for $100 at Summit aren't true fuel cells. They are just fuel safe formed plastic container, but don't have the bladder which is the true safety part.
1971 240Z - LS1 swap in progress. Just need to: get wheels, drop the car from the rotiserrie, install the motor and trans, rebuild my dash, put in a new interior plus a few more odds and ends (about $10k in incidentals). Should be on the road before my 5 year old heads off to college.