jp -
It looks like your interior was the same or similar to my 73 2L's #31 Beige, but not sure if your carpet was the regular OE Tan/Beige or the OE Dark Tan - which looks like oatmeal with a mix of the tan & brown loop pile yarns in a speckled pattern, but it looks just a tad darker than straight tan & therefore didn't show the dirt as much.
You can see the difference at Jeff Bowlsby's pic link below between #502 Tan & #503 Dark Tan (but the camera coloration is off) from the 74 MY (he has no 73 MY stuff....yet) -
http://bowlsby.net/914/Classic/zPF_74F3.jpghttp://bowlsby.net/914/Classic/PaintFabrics.htmYou can rill out those metal rivets with a small drill bit which is about the size of the dimple in the center of the rivet or slightly bigger. Not too big & keep the drill/bit straight in all 3-axis - or you'll enlarge the hole too much & the new plastic rivets will be loose.
Plastic rivets were original & still available in clear, even from Porsche (also used in 911/912/etc. so they keep them around), but the originals were white for the aluminum thresholds & black for the black plastic thresholds.
I think they used the metal rivets over the years - even at Porsche+Audi dealers back in the day, because they were readily available & seen as stronger - so seen as an improvement.
Now to the "while I'm in there" part....
So while you're drilling & removing/replacing rivets there - get some extra rivets so you can do all of the rivets along both rocker panels, then unscrew the slotted cheesehead screws along the bottoms (or they may have substituted other screw types).
Then remove those rocker panels on both L & R in order to clean the crud out from behind them & to inspect your longitudenals behind them for rust damage - you'll be surprised how much dirt & crud gets up behind there - a supposedly sealed space, especially on the right/curbside.
And if any rust, there's yet another project you'll want to get them repaired by yourself if you're a competent welder/body worker or by a good body shop, because those are the 914's main structural elements - "frame" if you will - long-wise along the unibody structure.
Speaking of drilling & replacing rivets - I'm hoping for a windless weekend so I can re-rivet some of the aluminum belly pans on our vintage 1960 Avion T20 trailer (like an Airstream) this weekend .... or at least before our next vintage trailer event in March!
PS - If I missed any of your questions, just post them again below.
The close up pix of your floor mat sections look like the Dark Tan, but the center tunnel section may be Tan - not sure from the pix, but if different - a PO could've gotten the dark tan after the originals wore out for less dirt show, or because the dealer only had that color.
When I got mine in `75 the OO had put in black driver & passenger floor mat sections

so I put brown/tan coco mats over them since they were 1/2 the cost of OE Porsche floor mats new - since I was just out of college a year or so & already eating PBJ & Mac & Cheese to afford my 914!
Also in looking at your Seats you'll have #500 Corduroy seat inserts, so your interior code would be #32 IIRC (don't have the old Porsche doc handy now - my #31 was with basketweave vinyl inserts like on your doors).
And looking at your floor sections from under the carpet, it looks like yours was L65K Ravenna Green originally (see links below) - so if you ever repaint, then you might consider going back to it since it & Delphi Green Metallic look really sharp with the Beige interiors!
http://p914.com/p914_paint_L65K_73.htmhttp://p914.com/p914_paint_73.htmIt was a Ravenna or Delphi Green with Beige pic on the cover of my
"Porsche 914 & 914-6 - The Definitive History of the Road & Competition Cars" by Brian Long that made me drool over any green 914 - being a blue car guy myself!

Also if you ever want to add more original looking alloy wheels to your 1.7 - the Pedrini & Mahle "Baby Gasburner" 4-lug wheels look very sharp (see the O&H Forum's nailed topic on OE Wheels & Tires for pix of both - I like the Mahles a bit better myself), or even Fuchs @L 4-lugs.
Or if you prefer period correct aftermarket wheels - both the classic & 80's repop Riviera 5 spoke/4-lug & modern versions of the classic 8-spoke/4-lug Competition wheel look alloys by Revolution, Enkei & others look great too. Or just keep your streamliner hubcaps if you like those best.
Good Luck!
Tom
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