How street able are these 340 stroker motors?

It truly depends on the rest of the combination.

the rotating assembly of a stroker engine is usually capable of enduring just as many miles of street time as a stock factory 340, if not more.

I would advise you to be careful choosing the brand of crankshaft, and always go for a forged unit if your budget allows.

A stroker engine will create more torque overall because of it's increased displacement.

Typically in a street car, the more "unstreetable" the motor itself is the more torque is sacrificed at regular driving RPM to create more torque higher up in the RPM range.

For example, a mild street engine may make it's peak torque at 2600 RPM while a substantially modified engine with poor idle vacuum may make it's peak torque at 4600 RPM and require a high stall and short ratio rear gears to be used on the street at all.

As displacement is increased, the amount of RPM required to pull sufficient air/fuel mixture through the cylinder heads to make a given horsepower or torque number decreases.

This basically means that if everything else is equal (cam, heads, exhaust, intake, compression etc) a stroker motor will be more streetable than it's stock stroke equivalent.

That being said, usually the reason why people go a stroker is because their budget allows for a motor to be built to a higher state of tune regarding performance than what would be "streetable" if not for the stroker.

So ordinarily a person building a stroker will be more inclined to go with the "big" cam and the "big" heads because they can simply get away with "bigger" on the street. They have a LOT more low end torque to start with, so a bigger sacrifice is more acceptable.

That's why most stroker motors you see are likely to be fire breathing, choppy idle beasts that are seemingly remarkably efficient at making big horsepower numbers.

At the end of the day though, "Streetable" means different things to different people.