[Baron Von Zeppelin]

71 72 73 year model 455 block - Code YC
With the partial 0 character leading the EUN. " ( "
So it might be the original block , but it is not an SD block.
We can help you determine if it is the original block.

71 400cid heads #96
That's a popular 455 build combo with those heads to bump compression ratio.

Intake is a 1972 model.

Appraiser didn't know his azz from a hole in the ground.
But you have a Very Nice Formula 455 in a great color combo.

The rivets on trim tag are not factory rivets .
By that time in 73 production they were actually using the bolt head screws instead of rivets.

The steering wheel collar looks like a corrugated drain hose was utilized as a sleeve.

[Baron Von Zeppelin]

The EUN on the block is extremely too low to be original .
That is a low count EUN from the beginning of whatever production year.

( 003286 is ultra early in a model year , but your car is ultra late built in 73 model year.

[Baron Von Zeppelin]

73 Fbody production didn't start until Sept or Oct of 1972 because of the 72 strike at Norwood..
73 Fbody production ended in July or August of 1973.
So your Formula was nearing the end of the model year with an 07B body date
= 2nd week of July 1973

W66 on the trim tag is the indicator for Formula Firebird.

[Baron Von Zeppelin]

The dashpad , metal dash , console would not be black with a saddle interior.
They would all be saddle tones.
The carpet should be much darker also.

Just little factoids to bring you up to higher knowledge.

I owned a 73 SD TA for 20 years with an untouched saddle interior.

[Baron Von Zeppelin]

The invoice from PHS will tell you things like -
If the car was originally built with the RamAir Induction option that is on it now.
That was a fairly rare option.

It was possible to order Orange carpet in 1973 , maybe it had that originally and he changed it.
If the Formula wheel was original it will tell.
And will tell which dealership sold the car new.

[Baron Von Zeppelin]

Here is an Invoice for a Navajo Orange 73 Formula 400 that was ordered with RamAir and Orange carpet.

[Baron Von Zeppelin]

Here are some block ID pics.

Pic one is the date code - at the back near distributor .
Usually can jam a cellphone camera in there with flash on and capture it.
I038 on this example.

Pic two is the block casting number - at rear of block on passenger side.

Pic three is the partial VIN - down low on front face , passenger side.

Since the car was out in Cali , the replacement block may be from a Cali built car.
Fremont cars will have the VIN in a different spot - up higher towards the top - on the same flat face - on passenger side.

455's have actual 455 in raised numerals cast on one or both sides - around freeze plug vicinities.