I really need some advice here

Yes the W2 will work on all LA engines. How the rockers get oil is up to you. Via pushrod or through block into head oiling. Pushrod length? Probably so but check anyway. A lot has to do with what W2 you have. And what gear it has.

You could have traction issues with a 300hp engine. Need put a label on it so quickly. Everything has a limit. You may even find your good parts not good enough for a upgrade in HP. It's easy to break tires loose on most anything. If I can do it on a late model 180 hp 318 in a Duster with 3.21 gears.........everything stock.... Minus wide tires and rims...

Beef up the chassis with frame connectors and such. There's a big differance in how things change. 1 change at a time.