Got some whittling to do

Just a whittle bit. Lol
Do you have a belt sander?

draw shave will work faster . Mark end of handle from inside of hammer head and proceed carefully from there. You want snug fit. Then cut slot for wedge when handle fitted.

Almost there

I like to glue the wood wedge , no metal wedges leave the top 1/4 inch proud of the head sand all the varnish off the handle and use boiled linseed oil (BLO) a few coats
after the wedge glue has had some days to dry saturate the end grain at the of the head with BLO as it helps reduce shrinkage and fit issues later.

Whittle more,perfect fit.

Almost there..I got it covered

Schrade and I got it done.

Ya also have some sort of bird crap between the hammer head and the flat bar.

It'll be fine...worked for 30 yrs so far. I make do with what I have...petrified duck poop holds good.

Not gonna say nothing….like Schultz!

mini grinder and a flap disc makes quick work out of fitting wood handles.

I like to use a rasp, but it looks like the knife did the trick.