[PeteLeathersac]

Both wronged parties need to fight separate legal battles making sure the perpetrator is apprehended and firmly dealt with first.
Do whatever's necessary to get the car back legally including fresh title in hand <span style="text-decoration: underline">dated after </span> any of the foolishness that went on.
Car home and title secure you can look at the car/parts/situation w/ fresh eyes and if you can help the father/son team w/ cash and/or parts back or agree on a fair amount to sell them the project, big kudos to you!
Good intentions or not, involving the father/son too early could obstruct the clear path necessary to firmly nab the crook and/or gain hold of the car and clear title so best proceed selfishly until the cards are in your hand to play whatever way you see fit then.
Best to all innocents involved, swing the thief from the highest tree!
[img]<<GRAEMLIN_URL>>/beers.gif[/img]
~ Pete