Jim - the 0.070" difference is very real. I am o-ringing a set of valve covers for a member here and he has the Indy EZ heads. The covers are unbranded cast aluminum valve covers. You can see the layout of the valve cover holes in this attachment. I tried these valve covers on my TF270 heads and NO WAY were they gonna fit.
From the numbers, it appears the unbranded cast covers (0.305") have the smaller Indy offset for the corner bolts (0.299").
Unlikely to fit on TF heads unless the holes are very oversize for a 1/4" bolt.
FWIW, The B1 original heads in my possession have an offset about 0.326". But that is using calipers and a straight edge from the other two holes, so it could be 0.005-0.010" error, IMO.
