Ill b glad to see any conversion done properly to a 1K. Yes there are rotor and other engine setups on 1ks but to no surprise we dont know hey they fit or whats been done to make it possible for it to be a common thing. So it isnt common and you wont be different by putting a heavy v6 in one as theyre all a mystery in this rare little gem. So before we say lets do something different whether its rotor or Ca18 or 4ag just make sure it doesnt upset its balance and we get can get the ones done with details on file. Remember a 1k is 650 kgs on average so be careful what demon you wish for it as it might just not handle, stop or outmanouvre anything but a 70s corolla. A datsun stands for fun for bucks and the fact its left many high tech machinery in the past gasping for breath around corners. remember a v6 has 30-60 per cent more weight than a 4 of same materials.
1Ks came 1,2,3rd positions at the 1969 Japan grand prix and that was with a 1ltr.
A wide torque range is better than a peaky one when you have little weight.