I may sound like an echo chamber, but FIRST make it a solid truck. If it runs good with the engine you have, hold off on any swaps until everything else on the truck is right, which you can do as you have done, a piece at a time as money permits. If you try getting in too deep all at once you are likely to end up with a parked wreck decorating your driveway.
If you do all the small fixes first you will have a very nice truck that will carry you through college or vocational training and into a solid first job. Then would be the time to do more to it. At that point you could get something cheap to daily drive while you finish it off like you want. Then you will end up with a great truck instead of a yard queen, or worse a junkyard queen. Good luck and let us know how you come out.