Miles

Edit: Perhaps he didn't lengthen the push rod as required for the 280ZX MC swap which would act like a missing reaction disk. He should check that the measurement first and if that doesn't fix the problem go looking for the reaction disk. When I lost my reaction disk I made a new one from a rubber stopper and used JB Weld to fix it to the push rod base permanently. Push rod length per the picture below is 0.53 inch or 13.462 mm from the flange. Note: you do not have to remove the brake pipes to adjust the push rod. Just pull the MC back and push it aside. Push rod adjustment

Yep reaction disk. Typically falls out while adjusting the push rod length to work with the 280zx master cylinder.

Use a strong adhesive.

This one?

No picture. Pick up a copy of: How to Restore Your Datsun Z Car by Wick Humble. Details how to disassemble, repair and reassemble the 240Z with detailed pictures not available in the FSM. I used this book in restoring my 72 240Z. It saved hours of researching. Can you post a picture of which seal you mean? I can look at my Z or look it up.

Again, what happens when the lock button is pulled up? Does the button stay up in the unlocked position? There is a small torsion spring that keeps the lock button up. If that spring fails the door will always be locked. https://www.zcar.com/forum/10-70-83-tech-discussion-forum/108890-door-lock-knob-not-staying-up.html

Lift the door lock button up. When you let go of the button does it just drop down and lock the door when you release it?

Google searched "vq35de 280zx" See: Z-Fever VQ35DE swapped 280ZX post below Includes videos! Z-Fever has a website which includes tech write ups on VQ35 swaps: www.zfever.com Looks complex and expensive. SBC or LS engine swaps into 280Zx cars have been done and install kits are available.

Search this site for "vq35de". Lots of data!

Keep searching and form a plan. Members will be more likely to help once you can lay out a plan.

It has been done. Search HybridZ for member projects.

Wilwood has a rear disk brake kit that features a rotor with shoe style parking brake inside of the rotor hat. https://www.wilwood.com/Search/PartNoSearch?q=D154 Rear Parking Brake Kit Has anyone come up with a design like this for the 240Z? WILWOOD D154 BRAKE KIT.pdf

Picture of R180 vs R200. Look under the car.