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53-56 F100 Engine/Trans Swap Trans Tunnel?

Discussion in 'Off Topic Hot Rods & Customs' started by Richard D, Aug 8, 2026.

  1. I am swapping in a small block and (don't hate me!) 700R4. I have the cab up on the lift and putting in a complete new floor, rocker panels, seat mounts, etc. I don't want to take this thing on and off frame again, I'm wondering if I should leave a space for a trans tunnel? Truck will be pretty low so I have concerns.
     
  2. Complete floor?
    Can ya bolt the floor to the ch***is with the engine and trans and modify before installing the floor to the cab
     
  3. I really don't want to. It's a pain getting it in my small garage and on the lift, had to drag it in here by hand. I have to make the floor in multiple pieces anyway, so I'd prefer to just leave an empty space in the middle and fill it later with a flat or a tunnel. Maybe that's the answer right there?
     
  4. I have a Jag IFS that will be channeled up 2" in the frame. Doing a mock-up of the engine in the frame, I'll definitely need a tunnel.
     
  5. gene-koning
    Joined: Oct 28, 2016
    Posts: 6,896

    gene-koning
    ALLIANCE MEMBER

    I've built a lot of stuff. Mounting the motor and trans on the frame, then building the floor over top of the motor and trans is the most simple way to get the job done. If need be, the floor pan you are building can be built in one, two, or more pieces, as long as you plan a way to put them back together after each piece was removed from the frame separately.
    The other option is to leave the cab floor out of the cab until you hang the cab over the frame without the floor, then weld the floor pan pieces and the cab tight together.
     
    vtx1800 likes this.
  6. willymakeit
    Joined: Apr 13, 2009
    Posts: 1,503

    willymakeit
    Member

    Any pictures? Im getting ready to do a Jag in my 56
     
  7. Ralphies54
    Joined: Dec 18, 2009
    Posts: 808

    Ralphies54
    Member

    Plenty of room. I have the same trans in my 54 behind a small block,cable shift no problem. Trust me.
     
    Roothawg likes this.
  8. Roothawg
    Joined: Mar 14, 2001
    Posts: 26,786

    Roothawg
    ALLIANCE MEMBER

    You dont need to do anything. I had a 350/200 4r in my 53. No modifications required.
     
  9. downlojoe33
    Joined: Jul 25, 2013
    Posts: 1,134

    downlojoe33
    ALLIANCE MEMBER

    I have the same combo in my 56. It’s pretty low. Unmentionable aftermarket front suspension, raised front spring perches on the rear, and a totally flat floor.
     
    Roothawg likes this.
  10. I have it mounted to the bottom of the frame now but I want it lower; I need to cut two inches off the frame and brace it up with some 2" tubing. I can take some pictures of what I have now if you'd like.
     

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