Hi Chris, that 39mm base circle might be to large for the 17mm stud lifters,you might be able to retip the exhaust valves and set the exhaust clearances that way without any shims,the inlet's should be fine with the appropriate shims.
Hi Danny, EN26 rings a bell. There is still a bit of work to be done to the crank before it goes in, I've given the instruction to do whatever is needed to achieve the result