Ayuh,..... Those "bolts" are aluminum double ended studs, which I doubt can be changes with the motor in place,.....
They go through the transom, 'n inner transom plate,....
Ayuh,.... Then it's gotta be torn down, to see why,.....
Bein' flooded won't cause a complete loss of compression,....
More likely, bad valve, or wiped out cam,....
Ayuh,..... I wouldn't trust the heads you've got, til tested, 'n rebuilt,.....
If one, or both are cracked, a set of Vortec's is the only answer,.....
At that point, the crate motor is lookin' pretty cheap,....
Ayuh,..... Yer gonna have a million dollar motor by the time yer done,....
Why, O Why, didn't/don't you buy a long block current issue crate motor,..??..??
You'd have a better motor, with more power, for a boatload less money spent,.....
Ayuh,.... Call yer local GM dealer, 'n ask them,....
It might be cheaper than you think,.......
As for the over-bore, any more than .040 leads to thin walls, 'n cylinder hot spots, which can lead to an early failure,....
Ayuh,.... Welcome Aboard,...... It'll be cheaper, quicker, 'n easier to drop in 2 new long block crate 350s, that to rebuild the junk you've got now,....
'm all the accessory parts off the 305 will bolt right on,.....
