Dan,
Welcome to the site, its an odd experience but when I started reading your post I thought you may be in my neck of the woods because the local high school had a Y block for their shop motor back in the 60's and 70's, my brother always tried to buy it off them because it had never been run, it was only disassembled and reassembled as a class project each year. (I wonder if they still have it? maybe I should stop by some time). By the way it was in Maine
I wonder how many schools used Y blocks for their classes?, did ford have a program to donate the engines to the schools as a sponsorship or something?
As far as the lifters you found. Be aware! There were some after market ones that did not meet the hardness specs and ruined some cams and lifters before the problem was found. make sure the ones you found are up to spec, Mummert checks all his for hardness or won't sell them.
I have original FOMOCO sets that could be reground if you need and many other parts also.
Good luck with the project!
Bill

55 Vicky & customline
58 Rack Dump, 55 F350 yard truck, 57 F100
59 & 61 P 400's, 58 F100 custom cab, 69 F100, 79 F150, 82 F600 ramp truck, 90 mustang conv 7 up, 94 Mustang, Should I continue?