Sounds like you got a great deal, Brian. I think the 1973 M110 with the extra 10-15 bhp and earlier body and bumpers is the most desirable of the series, although the later cars were more refined with some subtly improved features.
If the engine has been maintained properly you might reasonably expect to undertake a valve job at around 200,000-250,000 miles--I've had bottom ends last over a half-million miles.
By all means let us know how you get on--best of luck
Tim Kraakevik
kraakevik@voyager.net