My dash and gauge cluster have been through so many configurations I’ve lost count. I wish I had had the foresight and financing to build my truck originally, in the exact configuration it is now. But this was an evolutionary process that too time to discover. Had I known how I really wanted it to end up I could have saved a lot of money and labor. Here's what it looks like now:
[IMG]http://img18.imageshack.us/img18/7480/a01al.jpg[/IMG][IMG]http://img801.imageshack.us/img801/5593/a02a.jpg[/IMG]But a direct answer to your question - the single main item I would have done differently if I had it to do over, would be to mount the main fuse panel behind the glove compartment along with modifications to the glove box to make for easy access.
My truck is wired with a Ron Francis kit. It was one of the best investments I ever made, particularly because it is so easy to rewire as changes are made (and there have been many over 19+ years). But I mounted it in the factory location to the left of the clutch pedal.
Now in my 60’s with three missing spinal discs and bad knees, any attention at the fuse panel is physically torturous. As we age, sitting upright in the passenger seat is far more enjoyable than bending and twisting on the knees trying to reach between the seat and under the dash.
A secondary issue was buying an Old Air A/C system. After two years of numerous problems and hundreds of dollars taking it to various shops trying to get it working properly, I ultimately tore it out and threw it in the garbage. I didn’t want to sell it to anyone else and have them go through the same experiences. Had it to do again I would have bought a Vintage Air system. That’s about all I can think of.