Landa MHP 4-3500 upgrade it to 8gpm?

Ive got the mhp 4-3500, uses a gx390 and a ts2021. Im sure the engine has busted a pin.
so, i got a gx690 and a tsf2221.
what do i have to change and to what?

that’s the power plant they used and the electronics

Or! Should i just throw a gx620 i got on it?

All I have to contribute is I use a 630 on a TSF2021 and get 3k/7-ish gpm. Works just fine for residential.

thanks, sometimes my wording isn’t great, but i don’t know much about the charging systems or the fuel injection to know if the coil and burner can provide enough hot water at a good temp for 8gpm. no biggie, I’ll eventually figure it out.