I think you could cap the return port just fine but the bigger problem is that the two pin harness connector will
not fit the four pin tank socket. (AMHIK!)
It seems only the 460 & 351HO trucks got the three port mechanical fuel pump, with return.
So the one shown (or one similar) would be correct for a 4.9 short bed/Flareside.
Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.