[Chris Burkard]

Fnchaser,

What model, year and engines is your Tiara?

MPH Gauge - No Tiara came with an MPH gauge from the factory unless you have a really old Tiara/Pursuit
Find the brand of your other gauges and order from your local Marine Supply Store (West Marine/Boaters World)

Power Trim Gauge - No Tiara that I know of has gauges except for the IPS boats and the gauges are built into the trim switch.
What brand are your trim tabs? - Go to your local Marine Supply Store and order based on the brand you have.

Bathroom Drain - Do you need the entire drain, or are you just looking for the stainless grate?
Same thing, go to your local Marine Supply Store and order. You may want to bring the old one with you to match up in the catalog.

Porthole Bezel - I'm assuming you have an old Tiara/Pursuit. If you have the old style black plastic portholes, you may be out of luck. I'm not sure those portholes are still in production. West Marine has a Catalog that you can look through and see if you match something.

Give us more information and I'll try and narrow it down for you.