273, could it be a commando and CAM question?

I have a similar combo, built a 273 HIPO from a standard 2 bbl 65 273.
The tranny is a 904 by 76, i.e. with big pilot button. The crank is forged so it has to come from a 340 or a 273 after 67.
Finished the motor will have the following spec:

D4B Edelbrock intake, 4 bbl dual plain
Edelbrock 1406, 600 cfm carb
Comp Cam cam part # 20-246-4 Duration @ .015 270/270, duration @ .050 224/224, .313 lobe lift, valve lift .468/.468, 110 lobe separation
Electronic ignition
Domed pistons, comp. ratio of 10.5:1
Spitfire headers

I have also switched to front K-H disc brakes.
Plans for the future is an 8 3/4 rear axle


The motor start will be done within a week.