1963 Plymouth Valiant Signet Convertible Restoration...HELLLP!!!

If your number one goal is to get it running by summer, the easiest (and fastest) way to accomplish that is to swap in another slant. Put a post in the Wanted section here for a running 225. Be prepared to travel within a reasonable distance to pick it up. Otherwise you're looking at a big, and long, project to use that 318/727.

Nobody has mentioned that your current trans and driveshaft is a Ball & Trunnion style , not a slip joint, so another challenge to overcome. Cooling, electrical, mounts, exhaust, brakes. All doable but going to take time and money.