Anyone know where I can get a metal .375L pitch timing pulley with 40 teeth, and a .625 bore with a 1/2 wide belt? I have found them in plastic, but I'm not to sure if it will hold up to the forces it takes to drive the knee.....I have found all the other pulleys I need in metal. I am wanting to drive the X&Y 3-1, and the knee 4-1.

try www.misumiusa.com they may have it but its a .63 bore
2006 inch catalog page 297 ive used them b4 there very helpful on the phone and there prices are resonable to

I live in the Great white north so may have a different supplier but yesterday a gentlemen gave me the Gates catalouge. From what I understand you need part number :TL40L050, product number: 7881-7054
which is 40 tooth, grey iron pulley. The bore range is .5" to 2.125 in. If you have a Gates belt supplier he should be able to order that and your adapter.
John

Try Mcmaster-Carr
They have a large selection of belts and Pulleys. You might have to bore the 5/8 hole or buy one with a QD bushing (taper lock bushing
Tim

check out econobelt.com

They seem to have 41 of those with double flange in steel.