Std dry weight for r1 is 390lbsFazer is 458lbsExpecting to be able to swap forks over without any mods is incredibly optimistic.Spring rate, then damping.I forget which model of gsxr 750 it is (iirc it's the k1-3, but don't quote me), but with a 10mm spacer the std spring is ideal for the r1 forks and plenty out there cheap.Take my advice or leave it, but remember I used to spanner for Jim Moodie and earned a living from translating rider talk to engineering solutions.
One of the biggest issues I found with the 1000 was its tendency to run wide on acceleration out of bends (Understeer). Trying to dial that out was extremly difficult, but once I got it sorted the bike is a joy to ride fast.I maintained the standard forks and used 10w oil and Wilber progressive springs. The reason I fitted Wilber progressive springs in the end was simply because I do a lot of 2 up riding and travel on very undulating roads (as Skippernick discovered ).