Yep, try to find a tachmeter for the big Ford 4.9 L inline six. That engine had a hp peak about 3600 rpm (EFI model). It was pointless to go much past that and at 4000 rpm you were just wasting time. Most aftermarket tachs went to 8000 rpm. I found the perfect tach on J.C. Whitney back about 20 years ago for my 1995 F150:J C Whitney, seems they had everything for every model. Looking through their catalog was almost as fun as scavenging parts from the junk yard.