Ryan - you dont wanna go an inch over 300BHP, otherwise tranny axle, torque arm and lower controll arms will live a very short life.
ditto for 350lbs ft.
a small block with much more than 350 bhp will really start to suffer on fuel economy, i'd aim for 275bhp, you should be able to achieve that with a nice streetable cam (go milde than you think 90% of people over cam)
dont forget, more cam doesn't just affect idle, even the peformance of the brakes will be reduced if you have a major cam in there..
dont go for anything that exceeds your needs, you will regret it. even 250bhp will make a massive difference in your car, but still retain decent economy and street manners. if you go the crate engine route (i strongly advise this) dont go for anything rated as 'fast road' or 'semi race' or 'street rod' you want a nice fat torque curve, and look for power and torque peaking at no more than 5000 RPM.
the power charicturistics of the LT1 engine work very well, while being trans and axle friendly, hmmm... that brings us back to that old chestnut, the goodwrench! (very similar engine - £1200 in the UK)
also remember that you will need to budget for a carb, a starter (good time to fit a new one, as mall block starters arent especialy long lived) and will need gaskets for things like the water pump distributor, and oil pan - none of which come with a crate engine.
using an engine around the price of a goodwrench, you should comfortably be ready to go for £2000 - and thats allowing for new belts, coil HT's and plugs.
also be careful, some aftermarket cams dont have the lobe for driving the fuel pump. the stock pump is perfectly adequate for 250 - 300BHP, if you need an after market pump, you are building an engine that is capable of emptying the float bowl quicker than you want - i.e. its gonna suck gas.
its also worth noting that vortec heads work exceptionaly well on mild small blocks, dont go for ally heads for what you want, otherwise you have to look into lowering springs (the car will sit nose up otherwise) - more ££££££'s
you dont wanna make un nesicary work and expense for yourself.