To rebuild or not to rebuild...advice!

[Buford]

I have a 71 2500 GMC Custom Camper. This truck was originally bought by my grandfater and passed down to me a couple years ago. I still have all the paper work (even original window sticker). The engine was rebuilt 46,000 miles ago and runs very strong, but.......that was in 1977! My problem is that although it runs good and the vitals are great, 33 years has not been so kind on the seals and it leaks all over my driveway. I was thinking of pulling the motor and just replacing the seals and gaskets but I'm not sure if I should just rebuild it while it's out. I'm waying the pros and cons. My biggest con is that you don't really know what your getting in a rebuild until it's broken in. I've had piles of crap (snapped crank after 16,000) and great motors. The current motor just sings down the road, and always has. I hate messing with something that works. What do you guys thing?

Thanks!