Something like this, you don't want to take a chance with. You get one opportunity to drill the hole in the correct place. 2 choices, get a copy of the 1966 assembly manual and look up RPO U73 Rear manual antenna. Also look at RPO U75 Rear power antenna, the holes should be in the same place but you can verify that. Second, get a copy of the installation instructions for the rear antenna and they should also have the measurements.
If you can't find the assembly manual pages let me know and I'll post them later.
1966 Impala SS
Please Visit our new site:
1959 through 1988* window stickers, car shippers, dealer invoices, retail sales orders and tank stickers, expertly reproduced, for most Chevrolet Models.