Yes, no cush drive and a big hole where the clutch was with the belt setup. The belt has steel cable running through it to provide flex but the stretch is nil (except for the modulus of elasticity of steel). Somewhat surprised there is not a belt drive for the pump. I think an offset sprocket is available to allow a wider rear tyre on a race bike.
Two ways to dowel the rockerboxes, using the outer two 5/16" bolt holes or the 1/4" bolts at the ends of the rockerbox. There is not enough material around the hole on the AM heads to use the 5/16" holes. The 1/4" holes can use used on either. The dowels are pressed into the rockerbox and slip fit in the head. You need a mill with a digital readout or CNC to do this properly.
As long as you are doing this you should spot face the three 1/4" holes at the pocket lip with a 7/16" end mill and use button head screws which have 64% more area under the head and less likely to crush the material around the holes.
I've always wanted to implement those things David, ever since you first described it to me. I've used 5/16" dowels on my AM head, no problem. I had my machinist drill through the rocker box and into the head. He then made and inserted sleeves through it, which protrudes and acts as a dowel. No chance for misalignment. Strangely enough the "Covseal" gaskets fitted over the dowels with no modifications.
I spot faced the 1/4" holes myself and used my own "button heads" as I couldn't find any locally. In addition, I drilled out the threads and used nuts and washers on the under side, to add some elasticity. I've only just tested it, but so far so good.