Tach dash question, need help.

[fatblockvelle]

I have a 1971 k5 blazer... Truck did not have a tach dash in it. I just got a complete dash that looks to be in great shape with no burn marks on circuit board. My question is.

Is there a way to tell if the truck the tach dash came from is a 8 or 6 cyl?

Is there a way to make it work if it was from a 6cly?

Is it as simple as swapping out the clusters and putting a tach wire and power on the gauge?

thanks for the help!!!! Anything else i should look out for