Engine question for everyone

[jadkins08]

First off a little background. I recently convinced my grandma to let me restore my grandpa's old farm truck that I rode around with him in for about 15 years. It is a 1971 C-10 Custom Deluxe Long Bed that originally had a 350. About 10 years ago my grandpa decided to replace the 350 (was having trouble with it) with a 307. The 307 had about 50000 miles on it at the time and probably has about 70000 on it now. It still seems to run strong and sounds pretty good, but it has developed an oil leak which my uncle says is around the master cylinder. I am trying to decide if I should just try to fix the leak and tune up the 307 or go for broke and buy a crate 350. I guess in a perfect world I would keep the 307 in it for 4 or 5 years and then buy a crate 350 when I have a little more money (Hopefully). What do you all think? Any suggestions, advice. Thanks and God bless.

Jeremy