tough decisions!
What "I'd" do....
1. 700R4 and drive her
2. 3.73 rear gear
3. If you still have the itch for a biog block, THEN go get it - I don't think you're letting the deal of the century slip through your fingers for $2500... You can get another one for that price or less, even if it is "just right' right now.
- since money is tight - do it in this order (even over several years - but in the meantime you have a cool truck) so that you,
Never duplicate your effort
Enjoy it along the way
Don't feel rushed into a decision to not let the big block slip away - there are more rats in the sea.
Here's why I say this: I USED to be a big block fanatic. Drove two of them for some time with TH400's. Always thought I'd never be satisfied with anything less. Got tired of having the feeling I could only "afford to go so far" on a trip before it became silly expensive, etc. Now, I prefer an old school small block any day. Guess my days of roasting the hides are over - will build a race car for that... Who knows, someday I may even havea truck with a 6. Oooo, not sure on that one yet
The above preserves you the option of keeping the 6 OR dropping in a small block OR getting the big block. Either way - you're gonna want the 700R4 (or a T5 or TKO if you like to row your own).
If you know already that you will definitely get a big block sometime, then go for it, move that to the top of the list - and just have slightly lousy mileage until you save up for that 700R4.
OR, consider this - JUST the big block + 3.23 rear or something like that. Big block can work great with lower (numerical) gear and you could really help your mileage in the process. Will still be more bottom end tq/hp than the 6 with a 4.11, but it won't be Mr. Toad's wild ride either.
So many options, so little money, so little time!!
The fact that you're still on the fence, I think, is that little guy on your shoulder telling you to bail on the rushed buy on the big block.
Good luck, either way, you can't go wrong.