What engine would you build for a Ramcharger?

Like the title says, of the options I have, what would you build. Mind you, this is a 87, daily driven about 100 miles a day, A/C, power everything. 3.21 gears, 31x10.50x15 tires. Has manifolds dumping into 2-1/4 true duals, HEI ignition, 2bbl carb. Has 140,000 on the clock and currently get about 15mpg.
I have a complete 88 roller cam 318, all stock. Needs a single ball hone, rings bearings and valve job.
Just picked up a 76, 360 from a boat. Low compression. No ridge, cylinders look great. Hone will clean them up. Crank may need cutting if one spot doesn't clean up. No heads for this motor, but thought of using the #302's off the above 318 with a @318willrun port job. I do also have a complete set of 1.88/1.6 valves I could have cut into the heads, but my thoughts is that it's not really necessary since its a low rpm ramcharger.
Option 3 is a 98 5.9 magnum that will need EVERYTHING and a magnum specific intake, which I do t have.
So for extra parts, an Eddy performer and a SP2P intake. Eddy 1405 and a holley 80457.
Cams I have a stock 360 cam and the stock 318 roller cam. I will retain my exhaust, A/C and HEI ignition. I'm not opposed to purchasing a new cam kit, just it needs to be one to maintain fuel milage, reliability and stock converter.
Hope I covered everything.
Thanks Paul
12 valve, P Pump Cummins