Transfer screws. It’s a commonly used device in tool rooms and machine shops.
Essentially a hardened set screw with a point ground or machined on one end.

Ron68 wrote:

Rudi wrote:

Transfer screws. It’s a commonly used device in tool rooms and machine shops.
Essentially a hardened set screw with a point ground or machined on one end.

In aviation, we called them "tittie pins". The head of the bolt had a sharp point or "tit" that would mark the center of the nutplate/captured nut you want to attach your material to.  Screw in you pin and position your new plate, then tap where it sits on the pin and you now have a mark to drill your attaching hole.
 

Okay, sounds good. I see Amazon has sets of them. My plan is to weld the 1" spacer on the plate, and weld the existing holes on the plate closed. Put the plate on my transmission jack, get the plate where I want it and lift the plate into those points. Hopefully they are sharp enough to make a good mark.

This is what I would do.

Use short pieces of double sided foam tape like used in arts and crafts or body mouldings.

Use the tape on both sides of a thick washers or spacers of your desire.
Attach to car over each rivnut with an appropriate length stud.
Install plate as desired.
Separate the washers/spacers from body and all will be placed exactly and still attached to plate.
Transfer holes to new spacer material.

I try to keep it simple to minimize frustration.

This is bear I plan on adding that to my coupe.

I think you may be trying to over-enginerrThe weakest area will always be the floor pans and even bolting 1" solid steel bars to them, they will still be the weakest link.  If your goal is to provide more clearance for exhaust, 1" tubing with 3 5/8" OD 3/8 ID tube spacers (to prevent crushing of the square tubing) at the three bolt locations will provide adequate spacing and strength that will be as strong or stronger than what they are bolted to.  I wouldn't bother eliminating the slotted holes in the plate either.  An appropriate washer will keep the plate in position just as it did for many years from the factory and it will be a lot easier to install working upside down under the car.

If you are looking for a substantial increase in strength, integrated subframe connectors will provide much greater strength than the plate.  In my case, i eliminated the plate entirely with subframe connectors and an X-brace - a lot more work but a stronger floor with a lot more space for exhaust. 

https://ibb.co/2g6KPqZ

Last edited by GPatrick (3/21/2024 8:01 AM)

I bought a set of transfer screws from LittlemachineShop.com. My concern was getting all 6 holes marked at the same time without the plate moving around while I hit it with a hammer and also getting all three pins on one side at the same height so they all mark at the same time. I guess if I got a couple holes marked I could drill them and bolt the plate on to mark the rest.

KeithP wrote:

I bought a set of transfer screws from LittlemachineShop.com. My concern was getting all 6 holes marked at the same time without the plate moving around while I hit it with a hammer and also getting all three pins on one side at the same height so they all mark at the same time. I guess if I got a couple holes marked I could drill them and bolt the plate on to mark the rest.

Yes.  In that case you'll need to mark and drill 1 and secure it, mark and drill a second and secure it, and then you can do the remaining 4 at one because it won't be able to move.  Unless I can clamp the pieces securely together to do all the holes at once this is how I do it. 
 

KeithP wrote:

I bought a set of transfer screws from LittlemachineShop.com. My concern was getting all 6 holes marked at the same time without the plate moving around while I hit it with a hammer and also getting all three pins on one side at the same height so they all mark at the same time. I guess if I got a couple holes marked I could drill them and bolt the plate on to mark the rest.

 
Use a jack under the plate to hold it up against the floor pan.
The trick is getting all the screws at the same level so all are in contact with the plate.

Last edited by Rudi (3/21/2024 12:04 PM)

Rudi wrote:

KeithP wrote:

I bought a set of transfer screws from LittlemachineShop.com. My concern was getting all 6 holes marked at the same time without the plate moving around while I hit it with a hammer and also getting all three pins on one side at the same height so they all mark at the same time. I guess if I got a couple holes marked I could drill them and bolt the plate on to mark the rest.

 
Use a jack under the plate to hold it up against the floor pan.
The trick is getting all the screws at the same level so all are in contact with the plate.

Yep, that's the plan. Get the screws all level on each side with a scrap piece of metal. Lift plate into place with my transmission jack and carefully tap it with a hammer.