I'm sure TB45 or 48 for that matter would be great but just too big. The TB's in standard form are pretty sluggish (147kw/180kw) so need a monster huffer to make big power.
The RB is a tight squeeze in the Skyline. I can't imagine it would be a straight bolt in affair like the RB30 (obviously a bit more to it than that) once you factor in a turbo or two.
So far my calculations tell me the RB30/26 will cost me around $5000-$6000 to make around 400kw at the wheels. That's me building it, utilising as much of my current engine as possible (head, manifolds, twin 2860 Garretts, etc) and it being a rock solid engine (forged pistons, I/H beam conrods, ACL Pistons, etc.
If you were getting someone to do it for you you'd be looking at close to $10000 I'd say. Or you can buy a R.I.P.S long motor capable of 1500hp for $15000!
Spool Imports sell their bottom end for $7500.