RB25/30's ain't that hard I just recently threw a big end on mine and replaced it with one I had under the house.
If you have the right belt and line all the marks up, providing the tension is correct, confirm they meet up again after a number of rotations. No problem.
You then need to tune the thing,
Stock 25 computer needs a fuel reg to bump the fuel pressure up.
If you haven't touched the fuel pressure you don't have enough juice for the thirsty 30.
I have never used an adjustable cam wheel on either cam other than the standard oil activated one(which has a blocked off oil feed of course)