You may have already posted it elsewhere but it wouldn't hurt to refresh our memories on exactly what you have now.
I believe your Champion is based loosely on a 16? Or was it an 18?
current engine and mods, drive, ratio, prop, RPM, etc.
From that, we can make some recomendations on what might be a good route to take. Maybe you're getting all you can exect out of your current setup, or maybe you're missing something simple that could give you 5 mph.
I'm not a Volvo guy myself, but there are plenty here who know their way around them.
Don
'01 22 Classic, 502/B1
And a bunch of other stuff
"If everything seems under control, you're just not going fast enough" - Mario Andretti