Horse power for 71 was 58 gross. That went up to 67, and last Shovels were rated at 69, and the early Evos were 64. But those are advertised numbers.
In my experience, the performance fell off from the early 70's to the the 80's, as the EPA started messing with things and the fuel went to crap. Shovels were built for gas with lots of TEL in it, and did not like unleaded gas.
I bought my 1979 Electra Glide FLH King of the Highway on Christmas Eve 2017.
Previous owner had her 27-years.
I'm 2001 he upgraded the drivetrain:
All new bearings in engine & 4-speed
S&S Super Stock heads - single plug 😣
Super E Shorty carb
Head Quarters Torquer cam @ 0.465" lift
Jim's Power Glide tappets
Taper-Lite push rods
+0.020" forged slugs
24- tooth front sprocket
True dual exhaust
From 2001-2017 he road 2000 miles!
I ride this bike everyday.
Starts, idles, and runs perfect!
Great mileage. 40+ on freeway runs.
And if I'm not worried about mph, she
jumps off the line with the 3.01 first