Before installing OD or a 5 speed I humbly suggest that you think really hard about the kind of driving you intend to do in this car. Unless you're spending a LOT of time on superslab highways at 65MPH++, the stock gearing will be just fine.
An OD or 5 speed conversion is a lot of work, and it's relatively expensive. Don't do it unless you're convinced beyond doubt that the majority of your driving will be at higher speeds, or that you'll need a lot more top end speed for some reason (are you racing Porsches?).
The stock gearing is perfect for the car, *unless* you have some unusual need for more top end speed, or sustained speeds above 60ish MPH.
Save that money and purchse some wire wheels or a leather interior (or both!).
Good luck, let us know . . . :thumbsup: