I have a 68 mustang coupe with a 289 and a c4. I want to get better gas mileage when im on the freeway as well as getting a manual transmission, so i was wondering what is involved in this swap? what parts are needed and how much it will cost me? another option i heard of was to use a four-speed and change out the fourth gear to get better freeway mileage. is this possible? and if so how much would that cost?