so my 74 chevy pickup has been bogging down when it gets up to around 40 mph and sometimes it wont even go past 10 mph. did a compression test,(v8 engine) and on the dry tests, the pistons produced around 120-130 psi. Pistons 3 and 5 produced 105 and 110. From what i read, it could be a blown gasket or a crack on the engine. Any suggestions or wisdom to offer is much appreciated.