I would use the entire frame off the 55. If there are no cracks anywhere,
the only place I would reinforce would be to weld a flat 1/8 plate under the
upper A arms mounting surface. Those two bolt holes almost always have
cracks or will get them.
Strip the new frame and clean it well for ease of inspection and for a
better looking paint job. Remove the large and small cross member that bolt
to the frame behind the engine. This makes is easier to clean and easier to
slide under the car. I wire brushed the rust off the areas that were rusted
and sand blasted some areas that I couldn't get into with a wire wheel. I
used POR 15.
Have the new frame ready to go before you  remove the old.
Now for the hard part.
You'll need at  six good jack stands. Five pieces  of 4 X 6 wood. Two just
long enough to fit between the frame members where the gas tank sits.  Two
just long enough to fit between the frame members right where the front of
the body starts to go up to the firewall. And one about 18" long that you
can use on top of your floor jack to give it more lift. You must get high
enough for the kick up in the frame at the rear axle to clear the rest of
the body when you slide it forward. It may also be possible to slide the
frame out sideways but I never tried it that way.
1. Remove the engine, trans, rear end, spring and front         suspension.
2. Remove the bumpers and their brackets, as  you want     to  make the
frame as light as possible.
3. I removed the front clip, but it may be possible to leave
    it on. You probably took the hood off to remove the          engine
anyway.
4. Make a careful note of the spacers under the front            fenders and
under the radiator support.
5. The car is already sitting on jack stands since you
    had to do that to remove the front and rear suspension.
6. Remove the same two cross members as the on the         new unit. Make a
careful note of the rubber and metal
    spacers used under two bolts on each side of the big
    member.
7. Remove the seats and carpet so you can get to                 the frame
bolts
8. Place the long 4X6 between the frame at the area             where the
trunk is flat and just before it rises for the         wheel well. Put the
jack in the middle and jack it up as
    high as it will go. Put a jack stand on both ends of the     wood, far
apart for stability but not to far or the base of
    the stand will interfere with the frame when it is
    dropped down.
9. Do the same in the front right where the body is flat just
    in front of where the little cross member was.
10. loosen all the frame bolts almost all the way off. It is         a good
idea to squirt them with a penetrate first. I             stripped a few and
they are hell to get to                     replace. Some are up inside the
frame With the frame     hanging, you can see the spacers and make a careful
note of location and how many. Some of the rubber         pieces may stick
to the frame and some to the body.         Feel around and find them all.
11. Support the front of the frame are remove all of the              frame
bolts but the back two. Lower the front to
    the ground.
12. Support the back of the frame remove the
    last two bolts and lower it to the ground.
13. Slowly slide the frame forward till one of the
    remaining crossmembers comes up to the stands. I         think it will
be the rear one first
14. Place a long 4X6 between where the frame was at the     rear and put
stands under it. Now lower the wood             that was supporting the body
near the wheel well.
    By repositioning the stands and wood you can slowly
    move the frame forward and out. The last position of
    the stands for removal will serve well as the first
position for inserting the new frame. DO everything in     reverse to
install the frame. Spend as little time
    as possible under the car till you have the new frame
    in place with stands under it. Work on concrete with
    good stable stands.
15. You may want to replace the rubber spacers. Some     are quarter inch
and some are eighth inch. If you can
     find some old belting material it works well and you         can double
it up

Good luck and ask questions if I forgot anything.
Alex M
---------------------------------

 Great instructions Alex. When I pulled the body off the '51, I took
everything loose that held body and fenders to the frame. Then using
sawhorses and several stout timbers, I lifted the rear of the body, slid a
timber under it and let the ends rest on two sawhorses that set on either
side of the car. (BTW, the front clip was entirely removed before doing
this.) Then I let the the body rest a-straddle of the timber.
  Next, using an engine hoist again, I lifted the front of the body tub up
high enough to get a second big board under it with it's ends on two more
sawhorses. Since I'd left the suspension and axle in place, I just rolled
the frame out from underneath the body.
   I'll have to see if I can find the photos I took as I was doing it.