I need help with scanning resolutions/sizes

I've not scanned negatives before for large format printing, but, alas, I want to make some prints larger than my darkroom/wallet will allow, so I need to scan a couple negatives, but here is my problem.

I want to make a couple 30x40s from black and white 4x5 negatives, and I have access to an epson v700 scanner.
All scanner quality issues aside, how should I scan my negatives? I know the scanner has a maximum optical resolution of 6400dpi. Should I scan my negs at an output 4x5 inches and 6400dpi and resize in photoshop, or should I scan them at like 300dpi with an output size of 30x40 inches? My printer (El-Co) asks that files be sized accordingly to the size I want printed at no more than 254dpi, so should I scan at 254dpi and 30x40in?

my negatives are portraits with tmax100 and txp320

thanks

The scanner has a real, ass opposed to theortetical, optical resolution of around 2200, thus, your best work routine is to scan at 2400/100% and save that as a master scan. You will then resize in Photoshop just before you sharpen. The routine you use is to go to the Image Size command and 1) uncheck the resize image box, 2) change the resolution to that suggested by your printer (usually either 300 or 360), recheck the resize image box and set your final output size.

Having said all that, I know you don't want to hear about quality issues but you may not be satisfied with the 30x40 print you get from V700 scan ...

you should also consider just doing a wet print, as it is cheaper than a professional scan with similar results. like what Ted Harris says, i also have epson scanner and the scanner's low resolution only allows for 11x14 enlargements critically sharp. You might be able to get away with 30x40 if you view from a large distance, but if you want a critically sharp 30x40 you need to get it professionally scanned or wet printed. I would go for the much cheaper wet print.

where would I go/what kind of money am I looking at to have a wet print made?
I've only really hand printed