I'm looking into a Fender Precision Bass from the 70's, very good looking and with a heck of a bridge and a nice pickup, but it has a MIJ Fender Jazz-Bass neck. I heard that if you put a jazz neck into a P body, it will have some bad results. What do you guys think?
Thanks in advance.
duff mckagan's signature bass is a precision bass with a jazz neck and i think it sounds just fine
Exactly what would these "bad results" be?

People put j necks on p-basses all the time. I'm doing that on my current build. Fender makes several models with this arrangement, and of course there are a ton of fender clones that do the same.
I've been wondering about this for some time.

Can anyone just confirm that the necks can be interchanged? Like the bolt on point is the same size.
"Rome wasn't built in a week"

"Yeah but when they built rome, they didnt go "hey look, there's a functional building" AND ****ING KICK IT OVER AND PISS ON THE ASHES BECAUSE THE PEASANTS WERE CRYING THAT IT WAS TOO GLORIOUS AND AWESOME."
im 98% sure that the necks can be interchanged. i really want to put a jazz neck on my squier pbass but i want a real fender not allpro and there arent many for sale everon ebay and they allways want too much for them if i can find one for under 150 im going to do it and if it doesent work out imma find me a jazz body i guess.

if someone has already went through the effort of putting it on there then my advice is just go play on it and find out how long its been on there for. if its been on there for 3+ months then whatever damage could possibly occer has already happened so if it checks out with you t hats all that matters. obviosly look at the bolts to see if anything is hanging off and check workmanship
ESP B-405,Fender American Jazz Bass(EMG J active pups and LEO QUAN BADASS II ) squire P bass(EMG P active Pups)),
SansAmp Bass driver DI
Ampeg SvP PRO Tube Preamp
QSC2450 Power amp
Furman PL8