I also run a 34-78 series yellow top optima, didn't modify a single thing, it fits right onto the stock battery tray just fine, and the stock hold down works perfectly. It is very close to the AC line that passes next to the pressure cap, but the 2 aren't touching. I did have someone looking under my hood one day say "thats the wrong battery for this car, it's too big"...I just looked at him and said "why?" because I honestly don't understand, like I said, it fits on the tray perfectly, the hold down works on it perfectly, it's not interfering with anything else, and I didn't have to modify anything to put it there...I just took it out of my 95 Caprice, put it into my 2002 2500HD, and then took it out of that and put it into my 2000 Z28...he didn't tell me why he said that, so I still don't know.