Everybody feels, or at least MANY, that they need a "big block" motor to make the car worth having.. The "more is better" orientation. BUT what gets lost in that thinking is that a LA motor can do the exact same things, just not as quickly. NOT to forget how much easier it is to change plugs on a LA motor than ANY B/RB engine, period. My '80 Newport was the first 360 engine I'd had. When I pulled the spark plugs to see what they were and how they were burning, My Craftsman ratchet, extension, and spark plug socket headed for each plug like it was a heat-seeking rocket! Much different that on my 383s, of either the '66, '67, or '70 model years.
And with that B/RB weight not over the front wheels, turn-in and general handling can be a bit better, too.
You might THINK you miss the torque of the B/RB engine, but at what cost? Do you really need to be somewhere 15 seconds quicker? While saving money on fuel, at the same time?
I suspect you'll be much happier with your "deal" if you just get it running and driving as well as it can be. Then maybe a bit of paint work, even if it's just to get rid of the surface rust and look decent. Mechanicals first, cosmetics as possible. Enjoy ALL the time!
As a side note, your friends/relatives will probably think more of you getting it running/driving well and driving it. Rather than immediately "trying to make it better" with a bigger motor. Change ONE thing, like the motor and it results in a mountain of other things that need to be changed to make it work right. Not like changing a Camaro from a 305 to a 350, by any means!
Back in the later '80s, Dick Landy was our guest at our annual North Loop Dodge Performance Team shows. In the seminar which followed, he stated that unless you were going to go "440", go with a LA motor. That sounded unusual, but when considered, a stroker 360 will be at or past the size of 383cid, in a lighter-weight engine of greater power. The 904 can be beefed/upgraded to handle the additional power/torque while not absorbing as much horsepower as a 727 does, too. End result, more power, lighter weight, and more "power to the ground". What's wrong with that? With quicker/easier spark plug changes!