250 hp was a 4 GC. I have seen mixed reviews on fuel line size for it but my experience (although it's all newer than 1964) has been 3/8" line on all 327's.
__________________
1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles
1966 Grande Parisienne, 396 1 of 23 factory air cars
A link that is worth checking out is the GM Heritage site for Vehicle Information Kits: https://gmheritagecenter.com/docs/gm-heritage-archive/vehicle-information-kits/Chevrolet/1964-Chevrolet.pdf
Go to page 61 in the PDF file for Fuel System info. It doesn't mention the fuel inlet size, but it does say the 250-horse has a sintered bronze filter in the carb inlet, while the 300-horse has a glass bowl with a paper element. The 250-horse has a square bore carb (Carter AVS or Rochester 4GC?) with a 1.06" primary / 1.25" secondary venturis while the 300-horse has a larger Carter AFB with 1.25" primary / 1.56" secondary. Manual vs. auto affects carb selection as well.
__________________
67 Chevelle Malibu Sport Coupe, Oshawa-built 250 PG never disturbed.
In garage, 296 cid inline six & TH350...
Cam, Toronto.
I don't judge a man by how far he's fallen, but by how far back he bounces - Patton
Well, looking in the parts book at least, I see where the fuel line parts seem to be different for 283 and 327, although it never specifically states 3/8" or 5/16". I can't imagine why there would be a difference in the fuel pipe clips etc other than the size though. Even the tank sending unit is different, although there it says with or except dual exhaust. Are all 300hp dual? Are all 250hp single?
__________________
1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles
1966 Grande Parisienne, 396 1 of 23 factory air cars
In the older than 64 x frames, the dual exhaust cars ran the line through the tunnel and under the passenger side control arm and were 3/8, single exhaust was 5/16 and ran down the outside of the frame at the rear and the inside at the front. If they had a different sending unit, the difference was likely the 5/16 or 3/8 line size.
__________________
63 Parisienne sport coupe (The Big GTO), black, maroon interior, 409 4 speed; former owner of a 59 El Camino, 63 Corvette SWC, 62 Chev Bel Air SC. 1963- Pontiac top selling car in Canada
Mahone Bay, NS Still not old enough to need an automatic