I don't know if the engine is in the car and you are driving it, but if so may I suggest getting another sbb and use that one for your rebuild that way reguardless of how long it takes to complete the project you can still enjoy your car. As another poster mentioned its your car so YOU do what you think is going to make you happy.
Lackluster performance with crappy gas mileage if you get one of those(sounds like). It probably only has 7.5:1 compression with the open chamber heads. It is probably max bored as well with cheap stock style low compression pistons.(just guessing) Get the build info from that guy before you buy one of those,like overbore size,what pistons are used,camshaft numbers,what rings,what year heads,the undersize of the crank,is it balanced and whatever else you can think of to ask before you spend any $$$ on it. Like Andy said,the power sounds VERY wimpy for a big block.GL Derek
As Derek mentioned, get the info for the engines you are looking at. Ask if you get oil pan, intake manifold , carb, distributer, carb, fuel pump, valve covers, flex plate/flywheel, harmonic balancer,water pump. Otherwise you have these expenses to add to engine if the ones from your engine don't fit. There is a big expense in the little parts. Oil and filter, coolant,spark plugs and wires, cap coil and rotor,thermostat and housing, engine mounts, belts and hoses, sending units , fuel lines and vacuum lines ,bolts and fittings. This stuff adds up fast also.
Based off the information I have gathered i think I'm going to go with a 383 stroker or a 455 big block.
both decent choices .both do require alot of work to change over to as little from 350 will go to either engine and the chevy will require a trans change.This will be a good learning experiance for you .many on the board here have done either or both of these swaps for we can offer extra info to help get it done.
The sbc route you'll also need to change the side the fuel line is on the frame,and a trans adapter or chevy trans. Both swaps will require new frame pads and motor mounts. Of the 2 swaps,the 455 would be the easier one,the 350 pulleys might work on the 455 and maybe the pulley brackets.(not sure though). The fuel line on the 455 is on the same side as 350,but you will probably need to change the front suspension coil springs to compensate for the extra weight.(with the sbc as well if it has iron heads and iron intake,but should be ok with an aluminum intake with iron heads) If you have aluminum heads and intake on the 455 you do not have to change the springs. If you do go with the 455 make sure you have '74 or older heads with the closed chambers or you'll have very low compression and get crappy gas mileage. I have a set of '70 455 heads with Poston stage 1 valves and bronze guides that are bowl blended ready to bolt on and a .020" overbored block ready to assemble. Also have several sbc blocks to make a 383,even have a couple sbc 400 blocks if you wanted a sbc 434 stroker. I have access to LS engine parts as well if you want to go that route,they make a distributor kit for them now that mounts in the front that would make it look like a Buick.:Brow: The location of where you live isn't in your profile in the upper right hand corner of when you post,if you were close to me I could help you with either of those engines,I have both of them in stock ready to assemble,and of coarse I could help you with a sbb 350 as well as other too. Or I could help you build your own through this site or via email or phone. Pick your poison.GL Derek
Thats cool,you should probably start a new thread in the "other" section for your build. I'll help all I can over there,people some times get upset about sbc tech in the sbb section. Whatever you build,make sure you do it right.GL Derek
