Some motherboards would allow previous gen mounting spacing, but I would suggest getting the 1700 kit, just to eliminate any chance of mounting pressure issues.
When I was searching about previous Intel gen blocks and 1700 socket, the description of the EK kit says, basically, to allow compatibility with 1700 socket, and lists the compatible blocks.
Unless cutting very close to thermal limits, pretty much all decent blocks would still perform well.
The only reason I ended up going with the specific one from EK is because I had to start from zero again, and it would match perfectly my GPU block.
But if you already owns the block, don't bother.