Right distributor for an engine?

I have a 1978 ford Ranchero with a 351 midland in it and when I had the distributor changed my camshaft gears teeth broke so I got that fixed and then 8 months later with only putting exactly 1,067 miles into it the gears broke again and I'm pretty sure the distributor caused this because it had unusual scrap marks on the teeth so even though I might be wrong what's the right distributor for this type of engine

As for answering the question - I don't know. Sorry. But I'm taking time to answer because if you already broke one shaft then maybe there's been damage to the cam shaft. That can explain why you only went a thousand miles before breaking another distributor shaft. You MIGH want to check the cam for damage.

Hope this helps.

'

Two things could be going on here. Roller cams require a different type of distributor gear if that is what you have.
Second, what type of oil pump are you running? Some high volume pumps put a "H" of a strain on the gear.
I bet the distributor is fine. Just need to change out the drive gear. Contact the cam manufacture with your cam part number and see what they recommend for a new gear.

A Midland? I think you're mistaken. There were Cleveland's, Windsors, and Modifieds. I doubt you had the wrong distributor since it worked that long. More likely the bushings in it were shot and allowed too much free play which ate the gear. Or the oil pump caused it. Just for your knowledge the 351M was a 400 Cleveland block and heads with a Windsor crank.