Hey Martin:

I bought a 6 blade 16" solid fan from Flexi-lite and ran it during the hot day on Thanksgiving last year. I purposely got stuck in stop and go traffic and it never got over 185. I took it off to try the same size fan with a clutch. It too worked good.

I'm running a 22" aluminum reproduction Mancini rad. Are you using a 26" rad?

I tried to run an electric fan on my old Charger and I had problems when idling (couldn't pull enough air). It too had an aluminum rad (Be Cool cross flow). It cooled better with a clutch fan.

Timing can be significant, even a few degrees could make a big difference. Try running 38 degrees total timing (without the vacuum advance). Running lean will also cause it to heat up. Try backing out the idle mixture screws a 1/4 turn each.