Re: 5.0 to 5.7
You can't convert a 5 litre to a 5.7, physically impossible. Blocks are different so... Casting # on the block. another way is to pull off one of the heads and measure the piston. Stock heads are different too. As for the gears, the 5.7 would usually have a numericly lower gear ratio than the 5.0. My 5.7 has a 1.51:1 ratio while the 5 had 1.6:1 That said, Volvo often had several gear ratios for a given engine. But in your case, adding about 2 to 4 inches pitch to the prop would be close.
