a 1640 will hangle a 6 row head with no problems at all...it is less horsepower than a 1660 of such. and depends on terain and enviornment if the extra horsepower is needed or not. if it is powered by a DT-466 it is about 2000-2500 bucks for a short block...if you go that route make SURE you send the head in and have it inspected. and expect around 3500 bucks for a complete overhaul, at least that way you know what you have in it.