Ashley was kind enough to send me some specs from a late 70s Centurion catalog, and suggested I post them as part of this discussion, so here goes. Specs in parentheses refer to the SemiPro, not in parentheses are Pro. Pretty well matches my bike, at least as far as the parts I know are original. I thought the crank was a Mighty Victory, but the specs list a Mighty Custom, and I don't know the difference, honestly.

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CENTURION PROFESSIONAL (SEMI-PROFESSIONAL) CATALOG SPECS, CIRCA LATE '70s

Frame Size: 21.5", 22.5", 23.5", 24.5", 25.5"
Frame: Tange Champion No.1 double-butted chromoly tubing, forged tip.
Lugs: Centurion Professional
Fork: Tange Professional chromoly tubing, forged end
Head Set: Tange Levin (Tange Falcon)
Handle Bar: Sakae World Custom-SL alloy (Sakae World Randonneur alloy)
Stem: Sakae Royal-ESL (Sakae Royal)
Brakes: Dia-Compe Gran-Compe side pull (same but black)
Derailleurs: Suntour Cyclone front and rear, Cyclone shifter
(Suntour Cyclone F&R, Finger tip or PDL-M down tube shifters)
Cluster: Suntour Winner alloy 13-24 (Suntour Winner steel 13-24)
Chain: HKK Gold (D.I.D. chrome plated)
Crank Set: Sugina Mighty Custom 42-52 (Sunino Mighty Compe 42-52 black)
Pedals: MKS UR-K-Custom (MKS UR-K black)
Wheels: Araya 27x1 1/4 Soyo tubulars, stainless steel double butted spokes
(Araya 27x1 1/4 alloy clinchers, IRC 27x1 1/4 GSW Hi-Racer tires
stainless steel spokes)
Hubs: Sunshine Pro-Am low flange
Saddle: YFC Professional Super Soft (Elina Super-Pro)
Seat Post: Sakae RY-PI-ESL (Sakae RY-PI)
Extra: Toe clip and strap, fully reflectorized
Color: Pearlized, Ask for selection (pearlized orange, blue silver)
Weight: Approximately 23lbs for a 23.5" frame


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LATE 1970s CENTURION SEMI-PRO GEOMETRY
A=23.5" frame
B=570mm
C=1010mm
D=420mm
E=600mm
F=68mm
G=73 degrees
H=73 degrees
I=50mm
Weight=21lbs