well, I guess the answers to your questions are more questions...
Rebuild:
1. what is your mechanical skill level? do you have the required standard tools you'll need? have you ever rebuilt an engine? are you just talking about replacing the chain related parts or a full rebuild?
2. are you just planning on doing the front chain, or front and rear? the rear requires pulling the engine, or at least the transmission.
3. how much time do you have? can you live without the use of this vehicle for a minimum of 3 days? figure on around $700 for parts and you'll need special tools to hold the cams in place.
Remanufactured Engine:
if you purchase a rebuilt engine, are you going to do the install yourself, or pay someone else do it? the cost of the rebuilt engine alone will exceed the value of your truck, plus in order to make your warranty valid, the engine rebuilder is going to require you to change other parts that may be perfectly good (water pump, thermostat, hoses, filters). add these to the cost.
how many miles on the rest of the truck? what kind of shape is it in? is it worth spending this much money on it?
in my opinion, a reman engine isn't worth it. if you have to pay someone to install it, it definitely isn't worth it. where I live your truck is only worth scrap value if it needs a motor, and maybe $1500 with a good engine. I just scrapped a 2001 SOHC (which was otherwise in fair condition because the front chain cassette finally let go.
it depends how much you LOVE this truck. you can find a newer V8 for the same, or less, money.