Yes, the indentions in the body were covered by the rubber bumper ends.  But, since the 280 doesn't have the indention around the bumper, it might hit the body.

Maybe these will help.  

Front bumper:  Hard to visualize if Compressing front bumper strut allows lining everything up by pushing entire bumper/filler/side rubber “cap assembly back toward body...where to drill fluid release hole in shock?  Even so, there will still need some type of transition pc to fill gap between mounting hole in bumper (hidden behind rubber trim with 6 small molded-in “rivet-Type”  screws) and some potential bolt thread hole in front body metal.... hard to figure out how any kind of bolt could be covered by those trim rubber though?

Rear:  please note last four photos.  Shows current “attachment” w/ driver-side shock pushed in....result of someone... never mind?. Compressed mounting on that side leads me to believe bumper and filler will line-up Ok in center when passenger side shock is (properly) compressed.  Here comes the However,  notice the large gap on sides...even with some forward movement of entire bumper while trying to avoid near contact with wheelwell raised lip...still results in a 3-4” gap between backside of bumper and (closeup photo of threaded  mounting bolt “hole” in my 280) body.  This is the most problematic issue in a finished conversion for me.  Any conversion pc. must allow for the offset mounting points existing between 260 bumper and 280 body (in any bumper position, using existing filler or trying flush fit .  Is this something any 240/280 conversion product could be easily modified to accomplish?

My sincere thanks to this forum, I do appreciate your interest, input...and patience.      Doug

I once had a website where I did a how-to on 260Z bumpers to 280Z bodies.

unbolt the big bumpers. 

There is a screw in the center of the bumper strut. Unscrew this. Now, with a drill and small bit or a sharp pick, puncture the membrane inside the strut. Push the strut back into its housing. Mineral oil will squirt out. 

The 260Z bumper will now bolt right up. 

Position the strut so the bumper ends fit the body correctly and put a tack weld to hold the strut where it belongs. 

Wow!  Great info.  Did you do this strut compression and keep the 3 rubber fillers on each bumper?  Most importantly,  what did you do for side connection (s) to side body??  Were you able to use just the single threaded bolt-to-body mounting?  What conversion did you use or make for that 3-4” gap connector???  If I get that item for rear bumper, I’m back in business!  Th front bumper will need side connection also but it is much more stable than the rear’s wide gap and long “floating”  sides.  I am super anxious to hear the most important piece of your “how-to !!!  Thank you??.         Doug

The bolt on the side lined up for me but I was doing a ‘78 280Z. YMMV...

I’ve had my 240Z since 1980 and this was on a 280Z I bought to be more of a daily driver. It was years ago, so many of the details I don’t recall. I think the rear? I had to drill a hole on each side to mount the floating sides. The rubber, I just bought new at that time. Probably can’t now...

Here’s the 240Z. I have many 280Z pics but I’d have to scan as digital didn’t exist...

Edited December 2, 20186 yr by conedodger

Conedodger,   I don’t want to beat this thread into the ground, however, I still have questions about how you bolted (?) the rear floating sides to a 280 body. Did you keep filler rubber 3pcs. &  use/keep the 2 outside rubber trim pcs? Did you use anything in between back of bumper and body?  How did you bolt bumper into the body...did you drill a hole through the bumper face and run bolt on in to the body...my rubber trim pcs. won’t allow a bolt head/cap under them.   On each bumper (about 4” from end) I can feel a small,short kind of plate inside the bumper with two (6mm? sized) holes in them but I have no clue how to use them in any kind of bolt mounting into body....not to mention the fact that these small plates w/ holes are already forward of threaded hole and will only move even further forward if entire bumper moves forward in potential shock compression.  Trying to keep my questions and posts shorter but I don’t get the missing link of necessary bolt-ups ,into or away from, the back of bumper and then bolt thread into body (can’t visualize using the 280 “mount hole” for anything w/out some offset insulator-kind of item.  This would still puzzle me in any custom fabricated conversion insulator/bracket.  What am I not seeing how you have accomplished???

Perhaps last question-  did 74 260 use same single threaded body mount as a 77 280?  If so, In the same spot?   Thanks!