When I later started buying my own D&D material (Holmes, then AD&D and White Box a little later,) I was surprised to discover a few differences. Wisdom was replaced with Piety, and the spell system I was taught was a spell point system. Clerics had Piety Points in addition to Piety, and Magic-Users had Magical Conductivity points. I know Magical Conductivity started at 1d6, but I don't recall how it was regained or how it went up with level. I don't know that I ever played a Cleric back then, so I know even less about how Piety Points worked.
What I do remember is that the spell lists looked a lot like the lists in the various books, except each spell level had a numeric range that went roughly like: 1st level spells = 1-2, 2nd level spells = 1-3. These were the spell point costs. Here's a recreation using modern dice notation:
- 1st level spells: d6/3
- 2nd level spells: d6/2
- 3rd level spells: d4
- 4th level spells: d6
- 5th level spells: d8
- 6th level spells: 2d6
You of course rolled the dice when you cast a spell and lost that many Magical Conductivity points. Aside from the bookkeeping, it's a lot less hassle than other spell point systems I've seen.
What I think would be easier, if someone were to use this system today, is not keep track of separate MC/PP point pools, but keep a running tally of points spent on spells. When this tally exceeds hit points, the caster has run out of spell points. That's a little easier on the eraser, too.