If money is an issue and if the swapped engine will be left pretty much stock, I would keep it L28. A stock internal L28 can handle the same boost a stock internal RB26 will take. Yes an rb will make more power at the same boost but. If you are set on swapping and going to keep a swapped engine stock, I would do an LS. No point in putting in an RB26 and running stock turbos, inj, boost, ect.