I used to think big cu inch was the way to go. Until I bought an ‘86 Monte Carlo Super Sport with a great running original 305 HO. Has a converter in it. Shift kit. Chirps 2nd driving it normal. Hooker headers with PYPes mufflers out the back. No H pipe. Just straight back. Sounds exactly like yours. It’s a little street machine and reliable. The 305 gets a bad rap but once you have a good running one in the right car/truck you just don’t know.
I have 87 monte carlo looking for headers and exhaust systems 305 sb. Where did you purchase? I put a 700R Trans with shift kit 1500 stall also. Did you buy shorty headers?