putting in a new engine

[christine]

I just got a 78 chevy s/b stepside and made a deal with my father that i could get it if a new engine was put in (luckily paid for my him). He wants to put a newer(like 99 or newer) 4.8L V8 as I am a student and the 454 thats in there right now is going to kill me for gas. Has anyone heard of someone doing this with an older truck, it seemed a little weird to me but i was willing to make any agreements to finally getthe truck, or does anyone have any better ideas of an engine to put in? all help would be appreciated