jack plate

bout to complete my resto on the ‘68. last step will be repower. i have a unique 18’ hull design as u who have seen my pics can tell. i’ve never really played with engine height etc nor have i ever had a modern outboard with more built in setback etc installed on this boat.(74 tower of power now) question is whats the general opinion of putting a small manual say 4" plate on there mainly for height adjustment? engine has always been mounted all the way down on transom and has always planed and handled good. top speed of around 40 with an old 150 17 alum prop. goin from the 74 to the 02 engine will gain about 50lbs and about 5" of setback to the prop