1 What modifcations needs to be done to put a big block in?
Assuming V8 now, you'll need to replace engine, engine wiring, upper motor mounts, motor mount insulators, modify the engine mount brackets, replace the radiator, replace the trans mission, modify the driveshaft, replace the exhaust system, and replace the 8" rear axle with a 9" rear axle. The BB cars also had bigger brakes, or the optional disc brakes, so they could stop. Other stuff too…
2 What company has the best prices on resto parts.
There is no one company. Different suppliers have different deals with the manufacturers. Also, there is more than one source for many parts, for example, you can get really cheap antennas that look identical to expensive antennas in catalog photos. Some vendors, such as Glazier's, either won't sell the crappy one, or they'll tell you the difference. Others go strictly by price.
3 last question for now where can i go to run the numbers on our car?
If you have the original warranty tag on the LH door you can learn a lot. Any more than that, you might have a "buck" tag under the hood on the fender apron, you can learn even more there. More than that, you'll have to buy a copy of the original invoice from Kevin Marti.