[kehstr]

if you ever plan on starting the truck i wouldn't cap the heater lines, just buy a 3/4 to 5/8 adapter, they are pretty cheap at most hardware of auto part stores. that will still let coolant flow through everything.
If you plan on taking the evaporator box off, i would pull that off first, so you can see how things come off, so you kind of have some ideas to how it will come apart. The evaporator box comes off pretty easy, with about 3 nuts, and about 5 bolts. The foamy rubbery stuff that seals the box to the cab, and the inside header box to together is really cheap, you can pick up a complete kit for $25 from lmc, and find it cheaper anywhere else. so don't be too worried if you ruin them.
hope that helps