An old car is not a 1995-2000
An old mustang is one from the late 60s and early 70s. They are the ones worth money. However, their safety features sucked.
My first car was a Toyota corona (late 60s model I think). It was full of rust and leaked oil. The mechanic jury rigged a tin can to one of the engine hoses to collect the oil that dripped out. Every few days we would pour the oil back into the engine.
I was coming home from work one day and got pulled over for speeding. The speedo read 64kph and I was in a 60 zone. The cop said I was doing 74kph. I said the speedo only said 64. I got a $75 fine and a couple of demerit points. Turns out the car originally came out with 13 inch wheels but someone had upgraded it and put 14 inch wheels on it. That caused the speedo to read lower than the actual speed you were doing. Gotta watch out for that with some cars. People put low profile tyres on or bigger wheels and the speedo can end up reading the incorrect speed.
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My next car was a 1974 XB Ford falcon panel van. It had a 6 cylinder engine and 3 speed manual gearbox (column shift). It was a lovely car and had heaps of room in it. I got rid of it when my friend put his foot through the floor. It was rusted badly in the floor.
Next car was a 1974 XB Ford falcon coupe. My sky blue Mad Max mobile. It disappeared under mysterious circumstances in 2015. Not fuplie happy about that. Can't replace it and if any turn up on the market, they sell for over $100,000.
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If you are going to work on the car, try to get one without rust. Mechanical work is relatively easy but panel beating takes a little more skill.