Charlie, if you can double your money with no additional investment DO THAT. Trust me on this, if the market exists now, go for the quick flip. There's nothing worse than sinking additional money into a vehicle and then either missing the market (which I doubt with this car) or just missing the price point. Price point is a big thing; the cheaper it is, the more buyers you'll be able to satisfy. That's my lesson learned.
On that 63' Porsche; if the market is good for that car, sell her NOW. Why? Collectible cars run their own demand cycles/ pricing cycles, many never to return to historic highs. That's because classic cars follow a demographic of the population. Essentially, the fat part of the bell curve that drives classic values is 50+ year old men with wealth/ means. We're not talking crazy money, but we are talking about a guy who has the means (IOW, he's not financing the thing and he'll wait for the right deal). The BIG thing is, these guys are all buying cars they wanted/ rode in when they were kids. This is what drove much of the Euro boom in the 80's, even with the obscene money paid for the run of the mill Ferrari 512bbi, was guys reliving their past. Yes, there are more than few "rare" vehicles that have pretty high demand throughout the boom/ bust cycles, but these are few and far between. Ferrari GTO's, etc. Still, these cars tend to drop a significant in the low demand/ money contracting times. They simply are still able to sell these cars though.
In the late 90's through about 2008, American Muscle cars became the "it" thing. A garden variety (and make no mistake, they're far from "garden" and simply kick ass!) 1974 Trans Am SD-455 would sell for just over $100K. Now, that car is lucky to get $55K for it or so. Likewise, Daytona Chargers (69) with the 440's were selling for well into the six digits...like $200K territory at the top, if not more. With the 426's fetching well into the 300K territory, the market has crashed recently. A seller would be lucky to get $125K for a current Resto Superbird/ Charger. What is cool about that car is it's the first Nascar to break 200MPH in 1970!
Run of the mill Chargers, 68-69, were running about $55-65K for a full rotisserie resto, and $45-50K for a decent resto. Shit, non resto cars were bringing $25K alone, so long as they were 440's R/T and numbers matching...we're talking wreck out barn finds here.
Now, those cars are brining about $40K for an excellent resto and $30K for a decent resto. $25K buys a pretty damn decent resto car...some $20K less than 2-3 years earlier. The same goes for all the muscle cars. It appears the gap between a rotisserie resto and standard resto has closed significantly. That leads me to believe price point/ money has moved down on all these cars but more importantly, guys are buying these to drive them....not store in a garage as a collectible.
Don't even ask about Euro stuff...its DEAD. Food for thought; what's a current vintage car that *might* become a collectible/ value later? I've done alot of figuring on this and came up with one car thus far; the BMW Z8. Back in 2005, we bought a Z8 for $92K with 2100 miles on it. Mind you, these were selling for $250-300K at their height from the dealers. We held it a year, drove it and sold it for $95K. That seemed like a pretty decent deal to me. Now, that car would be worth about $110K-115K depending on miles. Inflation adjust it and you lose, but still, that's the only car I've seen add miles and value at the same time, of recent vintage. Take the AMG/SVT/M line/ S line/ Ferraris/ etc and none of these have any staying power in terms of value. I'd think a CLK63 Black series would do better than lose half it's $135K value in 4 years, but they just must have made too many of them.
My next pick for a value car/ possible collectible 10-15 years down the road; an E63 Wagon. They made very few of these, imported less than 500 into the states and they lap faster/ better than their sedan counterpart. It's possible...
One more thing to note: Collectibles below $20K have held up quite well. In fact, your run of the mill Trans Am has seemed to creep up a bit in value lately (for a well cared for car). That tells me this whole game, just like the used buyer market, is severely price point dependent. In the standard, ordinary used car market, $30K is the extreme threshold, with $25K and below being the sweet spot.
Totally too much info, but I was typing anyway...
nice Porsche! My dad used always say he kicked himself for not buying one. He was the original owner of a '63 VW bug...said that at the time he bought it, he had the cash for either the Porsche or the Bug and bought the Bug. Had over 1 million miles on it, went through 3 engines but still had the original transmission. 
