1. Wiring is simple. Have a friend help, get a book and dive into it.
2. Get rid of the Olds. You'll need a new PTO to pump shaft and possibly coupler end to PTO
3a. Thats up to you. Extending the tongue seems fairly easier and cheaper than a new trailer.
4. Summitracing.com
5. Ditch the coil, add the HEI, one power wire to the HEI for IGN, and one wire to the TACH, time it and go.