Unless your problem is air in the line, manual brakes stop as well as power, you just need to press a little harder. Your problem is probably that you are not used to pressing harder. I have never had an issue using my manual brakes.
I assume that when you are talking about 'bias-ply' you really mean 'bias-belted'. Bias-ply's are not that good and should be avoided. Bias-belted are ok to use. Radials will handle better than either.
My base 70. Mostly original or restored to like original. I'm the original owner, factory ordered the weekend they went on sale in February, delivered in early April. I couldn't afford many upgrades but it does have the F41 suspension upgrade. Got its 3rd (and last) repaint about 4 years ago...
I keep my limited use Camaro garaged and covered. I ordered a Covercraft CA16PD, size G3, 8 years ago (I got it at that time through JC Whitney). Its a poly/cotton cover.
Covercraft Industries - Custom Fit - Covers for Your Car and Seats, Sunscreens and Bras.
Been very happy with it.
You asked if numbers matching matters and it does. There is value associated with numbers matching. That doesn't mean that a highly modified car wont necessarily sell for more. That is comparing apples to oranges. Numbers matching matters when comparing similar cars, not modified cars which are...