on your original wheels, what is the bolt circle diameter?
And the diameter of the center hole?
To remove the tire from your wheels is there a removeable smallish ring or two that makes up one lip of the rim? Or does the rim come apart in the very center, the flat part between the two lips?
The first type are "lock ring" wheels, and are OK and safe if in good condition. The second type are "split" rims, and much more dangerous to play with or use.
Grigg