The 904 will require less hp to operate, keep that trans. It’ll save you from headaches.
W/the 3.21 gears and stock tires, a cam between 218 & 224 @050 is as larger as I would go duration wise. The 224 would like more stall than stock for sure. 26/2800 or more gear.
The 218 will make power to about 5K with stock heads. Upgraded heads will allow another nice and usable 500+ rpm to about 5500 rpm.
The 224 is like above, just add 500 rpm. Power to about 5500 with stock heads, upgraded heads will add another 500+ rpm to allow 6,000 rpm.
