Re: got me a project...newb need some help..with my engine
never mix and match used parts in an engine without knowing the tollerances. Has the crank been re-finished, if not, take the crank to a machineshop and have refinished. they will then get you the proper bearings. however you have to determine what version of 350 you have. 1-piece or 2-piece rear seal. the 305 was a 2-piece rear seal motor.
you have a pile of parts from two engines in a state of semi-assembly without knowing what you have. before you even buy anything, you need to know what you have, where your starting from. you will need to identify the 350 block/heads. if you can not, I suggest you at least talk to your local machine shop to identify the parts. from there you can then go thru the process of planning the re-assembly.
swapping cams from one motor to the next can be done. usually involves buying new lifters. however at that point, why not just buy a new cam and lifter set.
you do have to use every marine part from the 305 - distributor, carb, alternator, starter, fuel pump, exhaust manifolds, thermostat housing, etc.
As far as the drive. that will need to be inspected prior to installing. I would replace the water pump, and pressure test at a minimum. if you suspect the coupler, or gimbal bearing, now is the time to replace them.