5k should be enough to buy it, drag it out, clean it up, change the brakes and get it to start if it's not hydrolocked. The rest of the money could go for a back window and maybe a nice drop. I wouldn't swap a V8 in there if it's gonna throw the exquisite weight balance off.
Keep in mind the transmission in at the back of the car. An engine swap is a hell of a project for a car we don't even know if whoever owns it is willing to sell it, if it's not a stolen ghost resurfacing.
My problem is I live far from there, it's not even sure if I'll go back anytime this year, and it's on a private property so I'm not going to post the address here.
I know full well most MR members are not fucking crooks but it's not my car, and it's not rotting on my lawn but if something serious starts taking shape then yeah we need to get a hold of the guy and see if he wants to part with it but I won't drive back there just to see if he's home.
It's in the Lachute area, west of Mirabel.