It is fun, especially a normal and common pushrod V8.
The newer engines with the much more complicated valve trains, I'd pass unless I had tons of time to learn it. I want to do another 351, I've done about four, but this next time would be with aftermarket Cleveland heads, and big open intake, EFI, and the late model Explorer accessories. Mix the old with the new, and save an old car. That's fun.
91 Mark VII LSC SE - soon OBDII and 4R70, GTC kit and 347, custom paint.
1998 Mountaineer, 98 Explorer Limited to soon add 4WD, XP8 parts, KB blower, paint, 332.
99 Limited mail vehicle, SOHC 4WD. 72 Ranchero 351 project