To transplant a V8 into your truck you shouldnt have to do many wiring modifications, dist./coil and alternator wiring are about it, make sure you check your existing electrical system, gauges, etc. for 6v to 12v conversion (was 59 a 6 volt system?). Where the fun part starts is the modifications needed for the transmission, driveline, shifters, motor mounts, radiator, etc. Depending on what engine and tranny combination you choose, this will determine how extensive your modifications. If you are on a budget I would suggest keeping with your 6 cylinder (I dont mind 6 cylinders, make a split exhaust, sounds neat), it will get you on the road faster. If you have a little play money, get a mid 60's 302 V8 with a C4, plenty of them around so parts and pieces are cheap and easy to get if you make a mistake. Good Luck and have fun, experiment with things, no need to think inside the main-stream box!