High Mileage Magnum

So, I have been searching for a 360 Magnum to drop in my ‘65 Valiant. There are plenty of old Rams for sale around where I live but they all have very high miles on them. (200K to over 300K) Today I went and looked at one that is for sale on the side of the road near my house that I have seen for sale for a really long time. I looked at the odometer and it read 286,000 miles but I went and knocked on their door anyway. The truck looks like it has been very well taken care of; the owner started it up for me and the engine runs beautifully. Becides the torn/cracked interior pieces it looks like a well maintained truck. The guy said that he bought it new in 95 and is only selling it because he got another truck (exact same truck just a bit nicer) He’s had it for sale for over a year so I think I could get a pretty good deal on it for the engine and just part out the rest. I have a friend that could recondition the heads for me at least and I know a really good machine shop that could do a full on rebuild to new if I want. Would this high mileage engine be a good route to go if I want to keep the cost down? Like I said, almost everything available where I live has high miles but this one look like it was well taken care of.
I plan on converting to carburetor set-up and doing a few small things to the engine.

I don't know man, as rebuilding and machine work plus trying to recon the OE heads seems like a pretty big expense right there.
2.5-3k miles is quite a bit, but I will tell you this.
I paid 500 delivered to my house from a private seller for a Magnum with 92k on it and on the inside it looked like 20k or even less.
Barely any markings on the bearings and very obvious cross hatching in the cylinder bores.
The Magnums have a very low wear amount than V8's used to have.
Put it back together adding a brand new set of EQ heads with 1.96 valves, Hughes springs and retainers, an Oregon cam grinders roller regrind and grand total was right around 2k for a 400hp/420tq screamer put together as an LA motor.
Can you come close to that with heads reworking and a motor rebuild?
My block came out of a front end wrecked truck, so you might consider looking for something like that instead of a running vehicle that's going to cost you more and have to rebuild it anyway.

Just a thought.