You are going to want to buy both of these puppies! Trust me.
Get the appropriate size for your set up.
You may need to be creative and buy specific sizes of driver extensions.
You may need to take things apart, hose, fitting, something....start with the easiest, then move on the the harder.
Put on some chill music
, have a sports drink and water
handy, and try to stay calm.
Many of us have been there before.
Also, what does you mechanic say about how the engine runs?
And, go on someone else's boat who has a Perkins and is happy with it, listen to it, decide from there.