I look forward to hearing how your engine build goes. Are you going to dyno test it?

My block was s/n 426-538 and yours is 426-536, so very close together in Ken's shop. I was happy with his machine work on the block. Bore, deck height, mains, etc.
I expect you will have to clearance the block for the pushrods, my 440-1 heads needed a little more then Ken machined the block. My head opening is traced, but I only needed a little with the grinder right where my pushrod was touching (look carefully at my pic for the grinder).

I may have told you about my experience with the oil to the lifter galleys. Back then his blocks had the oil going around the rear cam bearing to the rear holes for the lifter galley. That special groove around the outside of the cam bearing was a nice restrictor and I didn't need any additional oil restricting for push rod oiling. I put an oil pressure gauge on the main oil supply galley (priority main oiling) and a second gauge on the top/back of the block while priming the system on the engine stand. Are you using spray bars for the B1 heads?

The one set of B1 intake spacers I saw had very small openings, and significant variation from one port to the next. A lot of material to remove, and the angled intake manifold bolt holes and port angles may need a hand grinder for final work after milling the spacers a little closer to size. This is what I saw (pic).