Correct if its an aftermarket "universal" id assume it wouldn't matter as it has tollerance to allow adjustment. Unless your buying a very shaddy universal block.
But what core only block are you looking at?
If your looking at full cover, there is almost 0 universal fullcover, because all it takes is one vendor to put this little resistor or cap in this stupid location to make your day a living hell.
IF you have a exotic block maker, like a SEA origin.
Your best lucky maybe hitting aliexpress, and looking for Bykski.
I have found some really hard to find blocks from them which eK would never make.
But make sure you inspect fitment issues, as i heard a lot of them are poorly machined.