I did a 66 I6 to V8 conversion, so I do not know the 67/68 but can say...........look at the parts store (CJ Pony/NPD etc) catalogs and see if the part/parts that you are working with are I6 or V8 specific, of the same reguardless. As for the 65/66, the parking brake system was the same, no differences. As for brake lines and hoses, again look at the catalogs. Are you just doing a suspension/steering swap from I6 to a V8 only? It took me a while to do my conversion, I was driving it during the transition progress. I can also say.....if you are sticking with the I6 and you install V8 coils and suspension up front, the front end will sit a little high do to the weight of the I6 being less. Yes......it will make it handle much better with the V8 suspension setup with the I6 power, but again.....the front will sit a little higher. Are you planning on insalling V8 rated rear leaf springs?