If you want an Alpine with a V8, buy a Tiger. It will be quicker, easier, probably cost less and will certainly be worth a lot more than a V8 conversion.
If you insist on doing a V-8 conversion, start with the knowledge that a short-deck (8.2") SBF engine with a toploader or T-5 transmission BARELY fits after removing the Alpine steering box and upper steering mechanism, fabricating engine mounts that "hang" from the original mounting locations for the steering box / steering relay lever assembly, moving the lower firewall back about 4", completely removing / replacing the transmission tunnel, modifying the inner fender panel reinforcement braces, modifying (or completely replacing) the front suspension crossmember to accommodate a front-steer R&P steering setup with terrible geometry and moving the brake and clutch master cylinders outboard by about 5". You will also need to cut holes in the front cruciform arms and notches in the rear cruciform arms to provide ground clearance for the exhaust pipes, remove the Alpine battery box and relocate the battery to the trunk and replace the Alpine rear axle with something that will stand up to "V8" torque (FWIW, a Ford 9" or equivalent will not fit without significant surgery to the rear floor / trunk panels).
A comprehensive side-by-side comparison of your S-V and a real Tiger would be a good way to start.