Here's the way I did it. There may be other methods but this worked for me.
It takes a skilled welder (not me) but the result is worth the effort.
The cab has inner and outer layer. The inner metal should be cut from the
headliner channel on the top, all the way down to where it ends, along the
door post and the seam next to the center window. The 3 window cab has the
same seam and door post, so the idea is to fit the inner panel from the
5-window into the corresponding place on the (former) 3 window.
The outer sheet metal layer remains attached to the inner layer, but the
cuts must be made in a different place - close to the glass area , where the
sheet metal is as flat as possible. Otherwise it will be difficult to weld,
if cut where the back of the cab bends up into the roof and on the sides.
You can more easily do this by making cuts with a sawzall through both
layers at the same time, and trimming with the corners out of the truck. Be
sure to cut oversize to allow room for the final cuts, which are done
through each layer with a die grinder or plasma cutter.
When the corners are removed from the donor cab, trim them carefully so all
edges are straight and clean. The make cardboard templates and carefully
transfer the measurements to the 3-window cab. This is probably the most
important part to get right - cut it a little small and finish by hand if
necessary.
The whole idea is to "plug" the cab corners into the empty area you've now
removed from the 3-window cab. You have retained all of the inner sheet
metal from the donor cab, and if the cuts are true, it will match up to the
corresponding points in the new cab.
It's important to measure repeatedly. Tack the new sections into place, and
butt weld the seams together. If done right, you will need very little
grinding and body filler, and the inside and outside of the cab will look as
if it came from the factory that way.
While you have the inner sheet metal removed, it's an ideal time to weld in
some 1/4" plate on the door posts, to be used as upper anchors for 3-point
seat belts.
Hopefully this makes sense. I studied the construction of the cab and
decided this would be the best way, rather than cutting the cab in half or
cutting out one big section with the rear window included. I hope to have
the welding skills someday to be able to do work like this myself, but I
ended up taking it to a local craftsman who does top-chops and other custom
work. It took him about a day and a half, and I did the body filler work. It
required about 1/2 cup of Bondo per side (inside and out). I'm very pleased
with the result.
Jack / Winter Park FL
----- Original Message -----
From: <Shurshot22@aol.com>
To: <oletrucks@autox.team.net>
Sent: Thursday, September 23, 1999 8:06 PM
Subject: [oletrucks] switch
> Anyone,
> I am starting to switch tops on my '51 cab which is a three window to a
five
> window deluxe cab top. My question is will these match up? How much of a
> project is it? Has anyone here ever done it before? Last but not least
what
> all should I know and how do I do it the easiest way possible? Plus I am
not
> sure of the year of the donor.
>
> Thanks,
> Mike
>
> '51 Chevy 3100 3 window / 5 window
> oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
>
oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
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