Good luck with your new project. If you want it on the road quickly then keep the original running gear. The 350 swap will require several modification which will put you well on the path to hot rodding it.
These would include, new transmission, new driveshaft, new rear axle, reworking the e-brake system, new exhaust, upgraded cooling, revised brake system, revised rear suspension and upgraded electrical.
If that is what you want then do not expect it to be a quick or cheap process. Placing a V8 in those trucks is not a simple process.
Have fun with it.
