75 series

Hey fellas im looking to but a h151 gearbox into my 75 series ute instead of a h55 just wondering if someone coukd tell me what that involves modification wise or will it just bolt straight in? Are the 79 series running this gearbox and if so can i just use a h151 from an 80 series and use 79...

New or good condition factory box with headache rack to mount on a 75 Cab/Chassis. Western USA or Canada preferred, but will entertain creative alternatives at the right price. :) PM me with info and thanks in advance!