Battery size for series 2 XJ6

I need a new battery for 1977 XJ6 with 1993 LT1 and 700r4 from a corvette.
I have been using a group 75 size battery with side connections (same as used in the 1993 corvette). It is a tight fit in the space on the passenger side by the windshield wiper motor, the original space designated for theXJ6’s battery.
I would like to get one a little smaller, any suggestions?

Patrick, smaller would be ok as far as cranking power, but it needs to locate well in the hold down bracket. Johns Cars used to make a nice stainless hold down frame, made from 1/2" stainless angle formed in a rectangle to fit the battery, two tabs welded on for the hold down rods. I still have one, could make one similar for a smaller battery.

what size crank amps are you using, that’s the main key

Thanks! Mine has 650 CCA.
Online, I found some good battery size charts. Group 70 size is 1 inch shorter in length than my group 75. Width and height are exactly the same size. That’s exactly what I’m looking for. I will look for a group 70 size with 650 CCA.

Thanks for the offer of making a battery hold down. If I can find a group 70 size, with the battery width, the same as group 75, my current battery hold down will work.

I bought this battery last week from Advance, fits the car and the hold down frame perfectly. I think a group 78, Same exact dimensions as the original hold down frame.

That is nice!

Prices for batteries are varied from the different parts stores. I have not found a resonable price for the group 70 size. Group 75 and 78 are in stock with the lowest price being $90.00.

While I’m searching I fit a group 78 from my suburban in the jag. I have a lot of wire harness and fuse box in the area, adding to the tight fit. I tried to photo my battery hold down at rhe bottom of the battery, but can’t see it with my radiator overflow tank and lines in the way.