hehe, for a minute there I was about to tell you wrong topic.
Is the firewall cromed? Polished or anything other than painted? If not, then its an easy job. If you can weld your 75% of the way there. Now I'm not sure of the firwall your speaking of, but if you can get a picture to me or direct me to one I could get a better understanding. Now if I'm thicking this correctly all you need is a peice of sheetmetal the same gauge as the firwall, a large tomato juice can (46oz campbles) and a welder.
Cut the sheetmetal to about 12" square. Cut both ends out of the can clamp one tip of the square flush with one side clamp the other end securely cut flush (flat) with the end of the can and bend the sheetmetal around the can cut the sides at an angle to produce a half cylender or more depending on the depth you want(or half of the can) Now cut a hole in the firewall the same shape, weld in the sheetmetal, point pointing to the sky. This will give you a channel to lift your distributor out and still look good.
Yes the can itself can be used but since it has the ribs in it you would have to do some smoothing. I didn't go into detail but if you need more help e-mail me, or respond through here, glad to help.
HK