Well I've tried to fit my hand behind the cluster but there just isn't enought play in the spedo cable. I can't even get to it from underneath. Would taking the dash pad off give me access to replace those darn bulbs?
As far as I know, taking the dash pad off will do nothing for you. I have a 68 tho. Have you thought about getting under the car and removing the speedo cable from the transmission? Then you should be able to pull the cluster out far enough to remove everything else. Just a thought. Also, while its out, maybe you can go and get a longer speedo cable from your local parts distributor. That is what I did.
I can sympathize with you, I also have big hands. I ended up taking my driver side seat out so I could lay flat on my back and trying to reach up into the dash from a more comfortable angle. No matter what a lot swearing will probably be involved it is definetly a tight fit.
I got my skinny 17 year old kid to do it for me. He had it done in about 3 minutes by just reaching around the cluster. I think he would have done it in half the time if I had waved 5 bucks in front of his face!! Good luck.
There is a grommet holding the speedo cable to the floorpan. If you pull the cable and grommet loose, you can get about 3-4 more inches of speedo cable in the cab. This lets you pull the cluster out more and unscrew it. It worked for me!