I just came across a perfect pic on CL showing the 74 bumper guards ("tits") side-by-side which illustrates the difference between the front & rear ones.
I decided to post it here because I've seen a few folks asking if they're swap-able, which they are not - IF you want them to look right!
The front ones are longer that the rear ones, & each is angled on the back side to relate to the angle of each bumper F & R - so that they sit right & are roughly level as they project out from the bumper. The fronts are longer due to the bow in the front bumper, whereas the rears can be shorter because that bumper is essentially flat L to R across a 914.
The F "tits" were used on 73 & 74 MY's 914's with either painted or chrome bumpers, while the R "tits" are from the 74 MY only.
Click to view attachment
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... so now you know a little more about "tits"!