Oh I got a lot of pushback way back in the day even with the sparse Mopar owners that I met, my first PK21 with the 440 6bbl one of the first accessories I install was a brand new Stewart Warner electronic tach, mounted on the A-pillar right by the spotlight and I didn't just stuff it in there, I made a aluminum bracket so it wouldn't go flying. First tire roasting session was left foot hard on the brake, trans in low and foot to the floor, speedometer needle straight up at 60mph and tach at 6,500 rpm... and held it there for a massive cloud of smoke (dumb kid) LOL Then when I was swapping out the 6bbl setup for a small 440 Holley setup I needed a 4bbl cold air oval cleaner like the 6bbl had. Go to want AD's and find one, slep on down to this guy's garage after work grab the air cleaner then he had a large box of dash gauges and wiring harness and asked if I was interested in it, saw it was a Cuda Rallye dash setup 150 mph gauge, wood trim panel, wiring and all switches, 50 bucks and I hauled it away only to just recently realize that the 6.5k redline tach in the cluster is a 440 6bbl & Hemi only item (and maybe AAR). I used the 6.5k redline tach as confirmation that 440's can do 6.5k and got back talk "that's a small block tach" Come to view a live Mecum Auction with the French 1971 Hemi Cuda and it has a 6.5k redline tach. (see below)
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And (I think) same auction a 1971 Plymouth AAR Cuda Tach appears to be 6.5k (not best picture)
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Standard 5.5k Tach with 7k limit.
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