Andy,
Good question indeed. Just because a block has sleeves, does not mean it should be written off. IF they were properly installed. Hmm...that sounds like a risky IF, doesn't it
?
What is your target HP on your new motor? Unless you are trying to make more than 400 fwhp, you should be fine with a regular 302 block--even a later model block (which is weaker than the older ones). Of course the benefit of the late model blocks is that they are already set up for a roller cam. If you are worried about block strength (or emissions legality), go with an older block, the best being the 'Mexican' blocks, which are becoming quite scarce but they're still out there if you are persistent. If you really want to make silly hp, step up to a used A4 or R302 block, which can be purchased for between $800 and $1400 depending on condition (finished machined, sleeved, etc.).
I also agree that the 331 will make for a longer lasting stroker. Then again, a stock stroke 302 will rev a little faster and a little higher, so it's all a matter of what you want. Personally, before you run into block strength problems, I think you'll have head gasket worries. Which is probably a good thing, as they act as a fuse before you really start breaking things
. It's been shown that an old Mexican 302 block with good fasteners can make upwards of 450 fwhp and live a long happy life.
Sorry for all the babble. One last point; perhaps the most important of all. The Boss block will have the canted valve reliefs, which will play havoc with your upper stroker piston rings, since the wrist pins (and hence top ring lands) will undoubtedly be quite high to maintain a decent rod ratio. One of my friends found this out the hard way
. $450 and 8 sleeves later, he was back on his merry way
. On the other hand, he did manage to make 470 rwhp with that bottom end (331 ci), a set of 2V cleveland heads and an S-trim Vortech...
Mike