Since then, Speedway has gotten them out for about $18 a pair: https://www.speedwaymotors.com/1935-1940-Ford-Mercury-Frame-Adapters,6671.html
I looked at the Speedway spacers, and they appear to be just spacers; the ones I made had the mounting bolts slightly offset, like the ones pictured in post 28. Another Speedway product that's not quite right? The price looks better though.
yes, the bolts need to be offset. i have two 34's with 59 motors in them, and the U spacers i made ended up being different heights! different by about a half inch. why? i dont know, but the motor placement is not forgiving. you must have the front pulley crank bolt centered where the hand crank loop is. any higher, the breather tube is hitting the firewall. any lower, the lower radiator hoses wont clear the front cross member.
I have a 34 5 window with and 8ba hooked to a 34 trans. I used a 35 truck firewall and the u brackets on the engine mounts. The one thing thats still a pain in the ass is the upper radiator hoses. Its a tough angle with a stock radiator. I replaced the upper necks with model A lower ones to help with routing the hoses. I'm still noodling it out.