hello I have a 1978 mercury 6cly 150hp long shaft model#1500 power trim serial#6200079 I need the lower unit,I been on ebay,and people tha sells their lower unit have said tha their lower unit for sell will fit a 75hp to a 150hp. I seen the pictures and they look just like mine,can you help me to define from how many horse power to how many horse power? I could use.and if is from a short shaft can I adapt it to my long shaft motor,even tha I have to make some modifications on the lower unit like changing the shaft?etc, or if is other lower units from diferent models tha I could use too. thank you again guys! 