I took my 400 SBC to the machine shop today. I need some advice for the rebuild. It is very important to remember that this is a torque motor for my COE and will not be revved past 4000 rpm. It has a very small .427/.452 split duration cam and 76cc heads. First - It needs to be honed to .040. (it was at .030) What piston is better, a flattop or a stock piston? The flattop will raise the compression in the 9.6 range. Will it run on regular pump gas with that compression? Will lower factory compression deliver better fuel mileage? Second - is there any real reason to change the rods to the 5.7 length or will the stock length work ok with the low rpm design?