Internal and external balance flywheels

This may sound stupid to some of you guys, but here goes anyway. I inherited the car I'm running now. Meaning someone else started the car and never finished. I tried to use what parts he had already bought to save Dad money. The problem is the car has a 460 crate from Ford which is an external balance engine. It has the counterweight in back of the balancer. I have been dealing with a vibration that at times causes the regulator needle to come unseated and flood the engine. Without pulling the engine or tranny how can I check to see if it has the right flywheel? It is a SFI flywheel but I'm beginning to think maybe it is internal balance. C-4 tranny.

If there is no dust shield, on the front of the bellhousing, behind the oil pan, look to see if the front of the flywheel is smooth all the way around. IF it is...it's for a neutral balance setup AND you will need to change it.

Don't forget about the counter weight at on the front of the crank. An internal balance requires the 'sleeve' while external has the 'hatchet'