I have driven many A-bodies and they were all around me growing up, but I was a F-body kid and never owned one until now. You are absolutely right that these are great cars from the factory even after 50+ years and this one made me grin ear-to-ear everytime I drove it. However, I like power, handling, great braking and even decent mileage and this car was bought and will be built to be driven and driven hard.
After I got the suspension and braking up to my desired level, I could have bolted a 200-4R or TKO600 to a built 389, 400, 428 or even a 455 and added a cheap throttle body injection EFI or an insanely expensive multi-port system and would have probably had more money in that setup than what I will have in the LS3 and Magnum T56 that I have bought. Seriously, 400 blocks alone in my area are asking $1,000 on Craigslist, just a bare block. Not to mention the LS3 will shave off 200+ pounds right off the front of the car. Once you add in the fact that the LS3 makes about 500 HP with the somewhat mild cam that was chosen by its previous owner, will easily run power brakes and idle all day in traffic with the AC running, has about 5,000 miles on it, will probably average in the low to mid 20's in highway MPG and cost me only $4,000, it really makes this a no brainer decision.
As I said in my first post, this was my plan all along and I wanted a car that was not historically valuable such as a GTO. I am not going to convert this one as I want it to stay a Tempest Custom and I plan to drive this car to car shows, go on the Power Tour and take it on vaction when I go so the reliability of a modern drivetrain makes more since to me. I know that that statement will open the flood gates of how reliable a properly tuned carb can be, etc., but I was raised in the fuel injection era and my first brand new car was a 2002 WS6 Trans Am when I was 24. I just did some basic bolt-ons to that car and let my uncle, who is a died in the wool GTO man, drive it and he said, "What have you done to this thing? It is faster than my old 67 Goat 400, and that thing was built!" Did I mention that car weighed about 3,800 lbs and got about 28 MPG on the interstate doing 80?
This Tempest should weigh about 3,200 lbs, have more power and will hopefully be on-par with that WS6 in handling and braking. Yes it is less aerodynamic, but it still should be one helluva fun car to drive!
Finally, the only cutting that should be done on this car is increasing the trans tunnel height, which would have had to have been done for just about any OD transmission other than the 200-4R, but I want a manual so that was not really an option. As for gutting the car, yes the drivetrain will be gone, but for now the only interior change will be the gauges, at least until I get tired of sliding around on the bench seat everytime I go around a curve! Also, I bought a nice car so that I wouldn't have to do paint and body work and I bet you would be surprised what I paid for this well kept 2 owner car that came with the original dealer invoice (bought new at a Pontiac dealership about 20 miles from my house in late 1966) and Protect-o-Plate...