engine upgrade

I have a 91 integra GS, motor has over 400K on it and looking at an engine upgrade. Thinking of installing a GRS (B17a1) motor or the
Si R (B18c). is there any motor mount changes needed with the B18? What about availability of these motors, and what about cost of these babies? I am pretty handy with a wrench and a laptop so i will be doing a self install, any words of advice


Thanks for any help in advance