as far as the two wheel drive goes check your front hubs.
if you can turn a nob to free or lock you have a part time front end and you have 2-wheel drive,if the end of your hub is a flat surface that you can't turn you have full time 4x4.
part time will give you better mpg but don't be to disapointed if you have full time the miles per gallon are not that bad(depending on your diff. ratio)and what you intend to do with the truck.
good luck with your new truck mine has given me good servive for a lot of years 1977 GMC 4x4.