Welcome to CHR!

Good deal or bad deal may depend on what type of dirt bike you traded away!!

Here's a few more suggestions:

Get us the numbers from the block and the heads. The casting number is typically on the rear (drivers side) and the engine number is stamped on a pad on the front of the engine on the passenger side.

Head numbers are typically in the middle of the head, but you need to remove the valve covers to get to it (you'll be doing this anyway - trust me)..

Look at this link for a real clear picture of where to find these numbers. GM Engine Casting Number Locations

The term "Power Pack" has been used for a lot of different heads - we really need the numbers to tell you what these heads started life as - I say that because depending on the head, they may have been machined during their life time up to and including different valves.

It's pretty tough to tell what you've got for cam (the "big cam" scares me a bit because it is almost always wrong and a typical rookie engine building mistake!) and pistons without major opening of the engine so let's work with the obvious stuff first. As has been mentioned, check the plugs and try and get the rear end ratio, get us some numbers and we'll combine a gazillion years of hot rod know how to help you get things sorted out!

Regards,
Glenn