You have to use a spacer to join the RB30 block to the awd sump - quite labour intensive.
I too have a cheap rebuild although frankly I would have liked to get rebored, forged pistons fully balanced etc.
For a cheap build you need rings, bearings and also better rod bolts. Use stock manifolds (although I don't know how much clearance you will have on the Holden) stock exhaust manifold will be fine for 300kw - you can run the w/g off the exhaust housing of the turbo. Use stock T/B and fpr.
the decision on re-using parts should be coloured by the difficulty of replacing them if they fail -so water pump and tensioners etc you can use them if they seem ok (but use brand new fixing bolts) but the oil pump is an engine out job and failure could cost you the engine. Depending on price a brand new R33 pump or an N1 with better gears. I picked up a Tomei steel h/g cheap.
Run in with cheap mineral oil and then use a quality synthetic from then on.