97 1/2 ton chevy truck?

I have 6 lug axles. How can I convert it to an 8 lug axle? Can I just buy an 8 lug hub from the same year and replace all of them? I am asking because i have 33 tires and rims, but they are eight lug ( I am planning on removing them from a 79 3/4 ton chevy, which is eight lug.) And i want to put them on my newer truck. Is there a conversion or am I out of luck?