I bought my first classic car '69 bird ~5 months ago for ~$30k. It was suppose to be turnkey but been running into issues ever since purchase. Took it to a classic car restoration where they did a tune up, new master cylinder, and a few other things which cost me ~$3k. I've had it for about 2 months since the tune up but it's been knocking. I called them and told them the knocking sounds like a new issue but they said they didn't notice anything and just keep an eye on it if it gets worse. I've been driving it since and it broke down on me today. Was driving when heard a loud pop, car shut off, and I coasted into a parking lot. I looked underneath and oil was pouring out.

What are my options now? or if any suggestions on next steps would be great. Engine WAS a "rebuilt" 400. But I don't want to put way more money into it without its value appreciating. I'm looking at some of the '69s currently for sale and wish I had reconsidered this purchase.

Thanks in advance for any suggestions or things to consider!

With out anymore specifics, sounds like you threw a rod. Most economical fix is going to be find a running engine that you can verify is good. [hear it run} and drop that in.
Hot rods are usually not money makers, they are money pits.

I see this scenario play out dozens of times a year since i work on these cars for a living. A guy buys a car with a nice shiny paint job and supposedly has rebuilt this and rebuilt that. In all reality what people are claiming is a rebuilt engine is just an 50 year old worn out engine with a coat of paint. Same goes with the rest of the car and the money starts flowing out like water.
To buy an engine that you know nothing about will send you down another rabbit hole.

Money pit is correct, deep wide mouth pits.

Yup, it sounds like a rod went through the side of the block. But best to find out for sure where the oil is coming from before making any decisions. Put it up on jackstands, crawl under and see what the heck. Maybe the filter blew off, or something similar. Wishful thinking but who knows.

Thanks. That was helpful.