I have looked everywhere and can't find stock length. I want to put on progressive 412 but need the stock length.

which sportster?
My wife's had 13 inch shocks, but they were too tall so I got a set of 12 inch from a friend that he took off of his sportster. Burly makes some slammer shocks that are only 10.5 inches

Go to your bike, take a tape measure with you and measure your shocks.
center of mounting bolt to center of mounting bolt, it really isnt that hard to do

Are different Model Sportsters with different length shocks .. The Longer the shock the more travel for comfort although progressive recommends not going over 1 inch away from stock length which can be measured as stated above ..

Well it's a xl1200c. the shocks measure 11 1/2 but who's to say they're stock shocks? It a 2005 so they could be replacements. Anyway I just ordered Progressive 412 shocks 12" long.

that aught to do ya

R's got 13.5"
I thought C's had 12.5"
Low models have 11.5"
just call a dealer and ask.

Correct. Lows also had shorter front fork springs.

Now the XLS-models...........

My dad had an '81 XLS



Now the XR models....

I ordered the 12" and after noticed that the stock length was 11 1/2" The shocks range from 11" to 13 1/2"
How much would 1/2" longer affect the ride? Should I send them back and get 11 1/2? They have already shipped but haven't received them yet.

11.5" will give the bike a tad lower stance. You'll probably like it more then the 12". The shock will have about 3/8" less travel. Make sure the tire clears the hardware and wiring as it will sit deeper into the fender.