The Henry J's used a KF Super Sonic head on a Willy's 4 cyl block, same block used from the 40's into the 60's on the jeeps.
The conversion came about as the original Continental engines were deemed under powered, so the Willy/ KF conversion came about.
97 Sahara, 74 Renegade, 72 CJ5, 55 Willy's (the Beast) Boss 302, 6:34 gearing, Bose 901 speakers.
God I miss that Jeep. Forgot the kinda Jeep, 80 SX4.