Adjustable Lifters

[bcatcmc]

Last year prior to installing my lifters I noticed cracking around the bottom edge of four of them, Speedway were kind enough to refund me the set ( after 2 years ) but could offer no alternative , neither could anyone else , seems like all lifters had decamped off the planet for awhile . I ended up getting 4 units from a tractor supply company ( I had the counter jockey run his vernier over them ) as fitted to N series Ford tractors. As my knowledge regarding Ford tractors could be written on the back of a postage stamp , the question is what years , and iff they were original Ford fittment or an aftermarket thing?