Ford Countour fans (v6..I believe '98-'02) are about as quiet as I've heard. I don't know how well they'll fit your radiator though. THey're virtually a bolt-in for fox body Mustangs. Dual fans. Had one on mine (427w) never ran hot-ever. Not even in the brutal summers we have here sitting in a drive through waiting for the soccer mom in front of me ordering 2 of everything for each of the team members. Mercury Mystique dual fans work well too (same fan set IIRC as the contour)
The fan set I got was very thin, came WITH the sensor and wiring, although I ditched it all and used an aftermarket controller. I got it brand new from Advance for under $200. Junkyards are even cheaper just make sure they work before you pay.
I also tried a Mark VIII fan and being a single fan, it was noisier and I had to trim the heck of out if to fit. Not long after, it locked up. Replaced the bearing and then found out about the Contour fans by accident (there was a fox radiator laying on the ground out of a 4 cylinder and a contour fan set laying nearby and they looked close to the same size), ditched the whole Mark fan setup and put the Contour fan in.
The MARK fan is a 2 speed, single blade fan. On low its quieter. On high it sounds like a jet taking off. I tested it before I bought it and I could barely hold onto it when turning it on, then when it finally got to speed, it wanted to take off like a helicopter would. They flat move a TON of air. The contour is a dual stage fan where in the factory configuration, one fan comes on when the engine temp gets up and if the temp doesn't drop the other comes on. If the A/C is on both fans are on. On my fox body (which had full Flowmaster "quiet" exhaust all the way to the tails...WITH cat converters), you literally could not hear the fans running. THe car was pretty quiet. I enjoyed cruising back & forth to the GF's house on the weekends with the A/C on and jamming to the radio, which did not have to be turned up all that much.
But as I mentioned, I do not know if it will fit your radiator. Fits FOX body stuff perfectly, which is, IIRC, 31x19. The only issue I had was that getting one out of a Contour with the engine installed was a pain. Never did get one out. If you can find one with the motor already dropped out, you're in luck...3 screws and it falls out. I decided to just buy a new one as I did not want a chance of a JY part failing on a long trip.