Slant 6 questions

Definitely do the Fuel line mod. Battery cable is a perfectly ordinary, plain, standard item -- buy by length. Much more interesting and informative than a VIN stamp on the engine is the engine stamping itself, which is below the № 1 (frontmost) spark plug.

Tune-up parts and technique suggestions in this thread. Carburetor operation and repair manuals and links to training movies and carb repair/modification threads are posted here for free download. Your son needs the three books described in this thread.