I know the "stump puller" 1st is not loved by those Speedster owners with more power (and not looking for stop light performance), but remember where the core transaxle comes from- an economy car with 40 to a maximum of 60 hp (real life production figures for the dual port 1600 were 52-55). Ist gear had to be able to get the car moving under all conditions (with 4 people on board), steep hills included, and it had to be able to run highway speeds as well. As has been said before, a custom mainshaft with a longer 1st gear is expensive- about $1,000 for all 3 pieces.
As Stan and Ed have said- for a car with a 2 liter (or larger) engine, going to a 3.44 r&p with the stock gearstack comes really close to a 356 1st/r&p combo, and at about 40% of the price of the mainshaft. Leave 2nd and 3rd alone, replace the .89 with a .93 (later stock, so shouldn't be that much) which gives the same final drive as a .82/3.88. You get shorter 3-4 spacing out of the deal as well, which will make the car ultimately more fun to drive, and since you're doing the rebuild anyway....
For those that are thinking the Berg 5 may be an option, they've just done a production run. No one knows if (or when) they'll do another run- it's years between 5 speed runs and I've heard through the grapevine that they might not be around that long. Rancho may take over production, but when it all happens will be the question. Even if you're not in the position to do it all right now, if you think a 5 speed is in your future it might be an idea to buy the kit now (if they have any left).
Carl- You were asking about the gearing for your 912- I don't know what the ratios are (never seen them published, although that doesn't mean they aren't out there somewhere). All I can tell you is that 1st is taller than what's in your Speedster, but you already knew that. Al