69 c-10 4bt or built 327

[blackdawn]

ok so i have been reading and researching for several weeks now and i have found a lot of information. now i want to get peoples opinions on what would work best for my situation. so here it is:
1969 c-10 halfton with coil rear
no engine no trans and will be changing tires and rear end gears to tune crusing rpm as needed
i drive about 18,000 miles a year and this will be my daily driver (90% freeway to work)
diesel fuel is on average is about 20 cents higher than 87 gas here
this truck will not haul anything 95% of the time, but will need the ability to pull a car hauler with a car on it if the need arises (dont really care what kind of fuel millage i get here as it will only happen 2 or 3 times a year at most)
my over all goal is fuel millage with some ability to tow when needed

so here are the 2 options i have in front of me:

have an engine builder budy build up a 327 from a 350 block that we will have a good amount of lower end torque ~370 ft lb's max
then purchase a 700r4 built by bowtie over drives
cost on this is about 3500-4k for the engine and another 2k for the tranny.

second option, find myself a bread truck, pull the 4bt, rebuild it if necessary, purchase either a 47rh or a 700r4 built up, redo brakes to hydroboost, adapt the power steering pump somehow for all of that, build the necisary mounts etc. i currently have a 4 core radiator so i dont think that will be an issue, and i will most likely get an intercooler.
all said and done im probably looking at around 6k for this package

that being said i am not interested in other diesels, 6.2 or 6.5 or the 6bt.

what do you guys think between these 2 scenarios, should i try and find myself a bread truck and head down that road, and pray my budget doesn't go to the moon, or stick with the priced out 327? best estimates that i have seen would be the 327 at 18-20mpg on the freeway and the 4bt around 25mpg on the freeway. so its about $700-1000 a year in savings on fuel with the 4bt right now. would like to hear opinions on doing it for the money savings mostly but i welcome the coolness factor of it. i don't plan to sell this truck, well ever since I'm going to sink more money than its worth into it body wise anyway.