Was thinking about how I don't like my high beam switch on my '90 Subaru daily driver. Thought reversion back to the floor switch on my scamp. I like the floor switch and think it's a far better way. I know this might not be slant six or a-body chrysler/a modern downgrade, but I think I might be able to locate the two while for the high beam switch and re-route them to a universal floor switch (or just a 70's era style floor switch. I think generally high beam floor switches are easier even for manual transmissions. My subaru is a 5spd manual.

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'73 Scamp (the girlfriend): 225ci super/6 2BBL conversion (Almost done!)
'90 Subaru, wagon (the wife): H4-cyl 2.2L

1977 Mercedes-Benz 300D, 5cyl diesel(For sale!)

Being from the rustbelt, I found that my floor switches would corrode badly, so I'd consider a new one rather than try to salvage an old one; the last one I bought was not expensive. The connector might be harder to find, but I found that the 3pin connector used on GM blowers was a perfect fit if you cut the plastic ears off. It ought not to be a very hard modification, but as it is related to safety be sure you do a really careful job on the wiring.

You might consider running the headlights via relays; then you need only run very little power through the switch. There's lots about doing that on this site.