The decomp valves themselves are also different lengths. The left side decomp valves are longer than the top right ones. If you have a left decomp top end now and put a top right decomp top end on you’ll need a shorter decomp valve.
I have put the shorter ones in the left decomp top ends before, and can’t tell a difference in performance, but that’s just me, and some may disagree.
I usually replace the decomp valves anyways when I replace a top end.
Just my $0.02