***Hypothetical Q---Thumpr/Whiplash cam in a 273?***

Run the smaller 318 version of the Whiplash. Should sound nice and run great! I wouldn't run the Thumper if I had a choice, they are good cams but I'm not sure if they are ground to take advantage of the .904 mopar lifter. Hughes are, and subsequently you get better ramp rate, and performance if you ask me. Especially if you use the adjustable rockers. Just my 2 cents. I run the 340/360 version whiplash in my otherwise stock 360'and it runs string for being 9:1, stock small valve iron heads, 750 carb and 3.23 gears. My buddy degree'd it in and it is sharp! Burns the tires throught 1st easy even with 275/50 drag radials.

While your at it convert over to a nice 4bbl intake and carb. 600cfm Street Demon is a great carb!