RV6 & 7 legs are the same pt#s
RV6 plans depict the dimensions to weld up an engine mount but if you went with a pre-fabricated mount, you would probably be buying a 7 mount.
Note- that if you have a 6 that had self fabricated mount, there is a good potential that you would have to deal with mount holes in the firewall that don't line up if trying to fit a pre-fabricated mount.
& yes, I've done this.
RV9 legs & mount are different.