Haven't doweled anything before so looking for some guidance and advice...

Need to dowel embossing male and female dies to a die set for alignment. The die set doesn't have enough opening so I used some 0.500 6061 plate to hang the embossing dies off the side of the die set. Seemed to work ok but need to pin the plates to the dies and the die set so things don't move. My plan is to line things up (dies have slip fit dowel holes for alignment between them), tighten up the bolts, then drill undersize holes through both parts. Then ream holes to get press fit on one side and slip on the other. Planning to drill new holes rather than try to use the existing holes in the dies to pin them in position.

Die set is steel. Embossing dies are steel (not hardened - I'm embossing thin aluminum sheet). Would like to make the steel parts the slip fit unless there is a good reason to go the other way around. Planning 0.250 dowel pins 0.75 long, about half in each part. For the aluminum press fit is 0.2495 a good size? For the slip fit how about 0.251? How about drilling these 1/64 undersize before reaming?

Seems like reaming the two parts with the small reamer while they are still together would be a good idea for best alignment. Then open up the steel with the larger reamer. I plan to do this on a mill with the parts bolted together. Do I need to finish one hole at a time and insert the dowel pin before going to the next hole or should I be able to drill all the holes first? Concerned about things moving.

I am planning to do this with HSS reamers since I don't expect to do something like this more than a couple times. For the current job I have 8 holes.