I have been carrying an extra fuel pump in my 1948 Chrysler's since 1974. Flat Heads love em.
I took Mary Ellen Rosk_ _ out to a Drive in Movie on Route 46 in Clifton NJ one night around March 1975,
She was from a good Polish Catholic family that lived in Hasbrook Heights NJ.her Dad had told me to have her home by midnight, (He was a Machinist)
and I thought he was serious so at midnight she was home. when I left her street ready to go under the George Washington Bridge and get back onto Rout 46
to go home my engine died. It was about freezing by then and a slow rain had just started. I took off my coat (because I had Satin Seat Covers) and laid under that 250.6
and changed out that fuel pump (in the pitch black) in 15 minutes. Tore off my wet shirt and put my leather jacket back on and got in and fired her right up.
Man I was sure glad those old Chrysler's had killer heaters, I stopped shuddering (teeth chattering) in about 3 or 4 minutes.
Always, Always, carry a spare fuel pump in your old Mopar Flat Heads. Back then I believe they were about $30, now I buy extras for about $68 on ebay.
Boy Life sure was fun when we were 19 years old, I still wonder about Mary Ellen from time to time, she would never let me past 3rd base, but we never saw too much of the movie,
"we were young but we were getting our share working on the night moves" If I were you I would find another mechanic $550 ain't exactly a fair price for a fuel pump change out.