Smaller class As do exist. By the age you are looking at many of the Cs have had enough rot in the cabover that they are junked. The Ford V10 replaced the 460V8 in 1998. The Chevrolet 454 was replaced by the Workhorse with the 8.1 GM engine. The small size you are looking at will not have an Allison trans. Early Ford V10s had self removing spark plugs on some until they added more threads in the heads. If you go larger you will have greater choices. Fuel mileage is improved with the newer chassis.
1999 Damon Challenger 310 Ford