Find out what block you have(phase 1 or 2). Phase 1 ended in 98 but some 99’s carried over phase one and some 98’s were updated with Phase 2 motors. Was a random run of the mill as to what you would end up with.
I would look for a phase 2 block with the larger rod mains(52mm) and 5th main thrust, Get matching heads and intake manifold as well!!! Port configuration is different between the two phases and the intake manifolds are required. Different bolt configurations at the bellhousing but bolt up to the EG series bellhousing just the same.
Look for a phase 2 RS motor up to '05. Use you’re heads/manifolds and swap over the CPS reluctor wheel/timing sprocket on the crank. You can use an Sti phase 2 block, but unless you immediately put forth the necessary components and tuning to turbocharge it you’ll be driving a low CR pig.
I have Moon’s shop car motor here for a rebuild now. Was a built 2.5RS phase one that failed(rod main, 49mm) that failed due to oil starvation on the dyno…
Lots we can discuss, all depends on how much $$$ you can throw at it to get it done at CBRD.