250 rebuild bore 40 over questions/

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I have a 1981 k10 that I'm planning to rebuild this summer just because its rather wore out and is very slow, (which I know is normal for these engines). I have the 250 with integrated heads (I'm pretty sure its the integrated head), and I want to bore it out 40 over. Will I have problems with overheating or will there still be enough cylinder wall left? Also and input about a good mild cam upgrade for a little more performance would be helpful as well. Thank you! My other option is to put a 327 block in it I have lying around, but I want to just rebuild the 250 to save money.