I want an old road bike to fix up that goes fast. Where do I start? I would like to get into road biking with some co-workers who have fancy new road bikes. However, I prefer to buy an older bike from the 70s, 80s, or 90s because I like fixing up  older stuff and I'm a little cheap.


Will I have a chance of keeping up with these people on an older bike if we have the same fitness level?
I'm looking to buy from Craigslist. What components/brands/features should I look for on an older road bike to know its of good pedigree and capable of keeping up with my co-workers?


Am I setting myself up for failure by buying an older road bike and expecting to go fast? Not sure if it matters, but I'm a fit 195lb 6 ft. 2 in. male. 

Thanks!
I have a similar outlook on bike purchasing - something nice enough to ride but cheap enough to afford.

First question - do you have a chance of keeping up with an expensive bike assuming equal ability?
There are lots of variables - but assuming this won't be an all out race you will do fine on a good quality older bike.  

Generally extra costs equals reduced weight.
Here is an article that compares weight with speed.
The bottom line is that a heavier bike does effect speed - but not very much. One extra kilogram on a 100 kilometer ride with mild hills = 30 seconds slower.  

There are other factors - bearing quality, wheel quality, tire type and inflation, etc. that come into play. The truth is - it's the rider that makes the biggest difference in performance.

Second question
The three key indicators when I look at a bike in that age range are brand, crank and condition.


I'm looking for a brand I recognize.
It's a long list and it boils down to - look at bike store bikes and not department store bikes. Bike shops back then sold cheap bikes but generally the worst bike store bike was better than the best department store bike (I'm sure there are exceptions but it's guide)
I'm looking for a forged aluminum crank.
Low end bike shop bikes had cranks with cotter pins or cranks that look like this:

The arm and the chain rings are actually two separate parts. In this case the chain rings are steel and the arm is aluminum. The arm is held to the rings with a type of rivet that allows flex while pedaling.   


Medium to high end bike shop bikes have a crank that looks something like this:

The arm and the spider - part that holds the chain rings is all one part - solid. This means less flex.  

Generally a bike shop bike with a forged crank will have a pretty good frame, aluminum rims and solid components. This will filter your selection into the medium to high range so you can focus on the other aspects of the bike.


Condition 


the obvious visual check for dings, rust, etc. 
Front tire is has tread and is not cracked/weathered
Front wheel is straight
front brake works well
Headset is correctly adjusted and smooth
Rear tire has tread and is not cracked/weathered
Rear wheel is straight
Rear brake works well
Chain ring is not worn
Chain is not stretched
Cogs are not worn front
Rear derailleurs shift well
Slip the chain off the crank and check for correct bearing adjustment
Remove the front and rear wheels and check for bearing adjustment  



An issue with any of these things is not instant disqualification from purchasing - they are all factors in how much effort you will have to put into the bike and how much you should pay.  

I'm sure there are other tips for finding the right bike but this is the broad brush I use to focus in on bikes of interest.