Wheel conversion for Pinto running gear

I have 14 inch Modern "Outlaw" wheels on my Model A Roadster Replica that I am trying to convert to a more or less real street rod. The suspension and steering are stock 1980 Pinto except for the addition of Heidt's 2 inch dropped spindles. I took out a link and a half of each front spring to bring it down an additional 3 inches for a 5 inch drop in front. The rear uses 3 inch lowering blocks. The stance looks ok but is too low for certain road conditions and will scrape sometimes at the point where the 4 speed standard floor shift transmission is held in place by the crossmember. I want to install 15 inch or larger diameter wheels on the car to improve ground clearance and get a better selection of wheel styles. I now have the Pinto 4 on 4 1/4 inch bolt pattern and want to go to the standard Ford 5 on 4 1/5. Replacing the rotors with Mustang 2 rotors will work and the installation of an 8 inch Ford rear end will work... Question. Is there welding required to install the rear end and how much if any expertise is needed to change out the rotors. Thanks for any advice you can give.