i will say go GM. of course i am biased. but honestly do not like the ford modular motors. they are great in a mustang but they seem to lack power in the trucks IMO. another is the rear diff. fords used two different rear diff in the half ton. if the 8.8 stay away. again work great in mustang but not in trucks lol.
price out the motors between the two. putting a motor in a 05 expedition soon. the motor was almost 2k alone from salvage yard. where as a chevy motor would be less than 1000 and that is on high side.
and working on them. GM is simpler than an old school pickup truck. the ford is one of the worst to put the motors in. have done it before so i know what i am getting into. but you think for a big vehicle there would be room.
and if you ever need parts you know JJs will have something for you. so logistics is easier if you ever need parts.
but the plus side of ford is they have a lot nicer interiors lol.
this would be the motor that i am talking about it is coming in today by truck. lol