I installed the big one with dual fans (can't recall the part number) in my 69 Road Runner. Yes -- had to drill some holes and otherwise fabricate a little. Re: the battery tray, I cut it down to minimum size and moved it rearward a few inches to make room for the radiator and overflow tank. And the module was very expensive. But it works great and I have no concerns about driving in hot weather, getting stuck in stop and go traffic, etc. Since I can still remember my 70 Road Runner having overheating problems back in 1972, it was worth it to put that entire issue to bed.