3" exhaust is pretty much overkill on any street driven small block. Regardless of what you believe, have read or someone told you, an engine does need some back pressure or it loses torque. It's been a long time since we bought pump gas that would safely run a 12.5 to 1 engine, and that's what you need, plus big heads and a lot of camshaft before needing 3" exhaust. Today you see lots of new pickups running around with too large of an exhaust system, all they are doing is making lots of noise that, in my opinion sounds bad, doesn't gain a thing in power, usually the opposite.
As far as the R&P it is a lot of work, even if you had a kit. The J car rack is just a start, you still have to locate it exactly so that you don't end up with a bump steer situation. Then believe me, I've done it, the steering shaft from the rack to your column has to snake thru your headers/manifolds and won't fit a standard clutch equalizer bar if you have a stick car, so then you are going to a cable or hydraulic clutch linkage. Your existing p/s pump is a lower pressure system than the rack needs, so you building brackets for a pump that will work, and the list goes on and on. When you are all done, you still have a car with a very antiquated front
suspension. The R&P is a neat idea, and the reason it is expensive is that the guy that makes the kit spent a lot of money and many, many hours of R&D before he got it right. As I mentioned, stay clear of the early design Unisteer manual system, they didn't get it right and many that were sold were returned because the steering shaft/u joints wouldn't work out without binding. Flaming Rivers first system had so much bump steer the car was unsafe.
Personally I have installed one manual R&P, at the same time I installed a RRS brand strut
suspension, total cost was about $3K! Yes, the car, a 65 convertible, drove and handled better than stock, but wouldn't begin to compete with a new Mustang. Since this was a customer's car, I did what he wanted, I would not do it for myself.