I found someone selling a brand new "4R70W/4R75W" transmission and converter for $900. He says it's for a 2007-2008 Crown Victoria or Grand Marquis.

What other information do I need to determine if it's compatible with my 2006 P71?

Pretty much any 2005-2008 2wd transmission will bolt in your car. Non-police cars got the short output shaft/short extension housing, CVPI and town car transmissions got the long out put shaft/long extension housing, so you will need to pay attention to that.

you might try to decode part # on the transmission ID tag, which is on the passenger side case. it appears 2007/2008 transmissions were essentially identical; https://www.crownvic.net/ubbthreads/ubbthreads.php?ubb=showflat&Number=1295031#Post1295031

Also the P71's got the 11.25" converter vs 12" one the civvy transmissions got. As long as the flex plate has bolt holes for both, you could use either. The smaller one has a slightly higher stall speed, and will give a bit better off-the-line go.

Pretty sure it's a civvy transmission, but I'm having the guy send me the tag info.

That's a hell of a deal if that is indeed a new transmission. I lucked into a guy that had 5 out of the leftovers at Ford several years back. Wish I could find more.

D