Tim
I had the same problem with my 40 block. I went with a -5 undersized chain and no more slop. Chain is tight and zero timing wiggle movement now. Have not had a problem with it in over 5 years now.

Oversize chains ?!?!?! All chains are the same - its the top sprocket that's oversize. Which allows you to replace worn chains with any "off the shelf" double roller chain.

NOPE, not true!
I had too much slack in my brand new cloyes roller chain set. I bought a -5 chain (undersized) and there is no more slack. I used the same new gearset I already had, but I replaced/swapped 1 new chain for another new chain. I believe the -5 chain may have had oversized rollers. That is the only thing I can think of that would take up the slack difference.

Strange that they don't list or mention shorter chains in their catalog ... and only reference undersize sets !!!!

Well, I may be in luck. Thanks to one of the Moparts sponsors. He says he can get .001", .004", .005" and .010" oversized rollmaster timing sets. I ordered the .004" set and should have it in 3-4 days(drop shipped to me). If he comes through believe me you, I will let you guys know who it is and how helpful he has been.

Well, I finally got the timing chain all sorted out. I have been dealing with Todd at Marsh performance in N.C. His supplier told him he could get rollmaster in several different sizes. Well.... they came back after I told him I wanted a .004" oversize that they could only get standard sets. He then ordered me a .005" Cloyes set (to be drop shipped)and said I could return it if it didn't fit(for a standard Rollmaster). When it arrived last Friday it was a standard set. So, I called him right away and he got the .005" set reordered. It came in Thursday and fit great!!!!! He is sending me a return shipper for the standard set they sent me. I would say he has gone above and beyond for a $125 part. Which by the way is an excellent price. I would highly recommend him to anyone.
Thanks Todd