1990 360 engine, trying to retrofit it to use a mechanical fuel pump.

woof. i'd say the water ingress is from there not being a carb on it... rarely do you get intake runners that funkalicious from a bad headgasket or cracked head/seat area.

we talked about this previously...

[URL]https://www.forabodiesonly.com...ical-fuel-pump-on-a-roller-cammed-360.566549/[/URL]

i'll echo what killer and 72 said: check what you've got cookin' first and if you do need the adapter hughes is the place to get it. for better or for worse.
The first time I discovered a roller 'teener on the job was a red '85 Dippy, the head gasket started leaking on #7, just past the warranty....not a ton of miles for the year on it either. Sam also had an '83 Cordoba, gold w/a brown top, all well maintained & garaged indoors.....one never knows.