||I recently got a 1984 Winnebago Chieftain with a 454. It turned over 83K miles this past weekend. It seems to be running pretty well. It took me down the freeway at 70 mph for 200 miles our first cruise, getting 5-6 mpg. Not cheap, but what is?
Anyway, I've heard lots of discussions about the 454 exhaust manifolds needing replacement because they overheat and warp or something. I found receipts for this one showing they were replace about 50K miles ago, and I've got no sign that they're in need of attention now (not able to hear exhaust notes leaking out with the engine cover off).
One problem i do have, and I don't know if it is common to 454 of this vintage, is that the fan belt that drives alternator/waterpump/ps pump is real hard to adjust for long life. An RV specialist told me it is a matter of getting the tension just right. Mine has been a problem--the old one let go last weekend, and I replaced it with one the previous owner left me, but it didn't seat quite right (looked too wide for the alternator pulley, but just right for the water pump pulley). Had to stop and adjust tension secveral times as it "wore in". I do see from the previous owners' receipts that it has been a problem all along--the original owner had the pulley replaced. Looks too small to me. Its amazing that it would go so many miles without someone finally fixing it! Rats. Anyway, good luck.