I agree, not necessary unless you are into strict originality. The valve works to only apply vacuum to the retard unit when the throttle is fully closed (slow idle); but you can just cap off the vacuum line and reset the idle without the retard. Don't forget to use the "static" timing value from the book, though, not the "4 ATDC" value. The vacuum retard is what pulls the timing back from 10 or 12 BTDC (I forget which offhand) to 4 ATDC.