[dfwright]

Don't get too wrapped up in the dimensions. They show you the dimensions on the paper, but you don't have to measure anything. Just cut the square out of the paper, trace it in the right place on the firewall, and cut out the traced lines. The bulkhead itself covers any rough places where your cut isn't perfect, so it's not seen after installation.

Also bear in mind this is the "Classic Update" kit -- it's not stock, and you need to decide if you want pure stock, or the benefits of the updated kit. I think the classic update kit is extremely nice, the quality is superb, and it offers huge flexibility in wiring your truck, all the way from mostly stock to heavy modern accessory use.

There are other non-stock considerations you'll need to deal with if you use this kit, since it is not set up for an external regulator, or for a stock points distributor. You can modify your wiring and use these if you want, but the classic update kit is designed to easily move up to an internally regulated alternator and HEI.