Which McGurk article is being cited? In the May 1955 article on the 261 McGurk measured 114 HP at 3500 RPM and 201 ft-lbf at 2000 RPM. That was on an engine dyno. In the June 1953 article on a 216 Frank measured 64 and 63 HP, respectively, at 3000 and 3500 RPM. The peak torque was 137 ft-lbf at 2000 RPM. These test were on a chassis dyno. A 1955 235 has higher compression ratio, 9% more displacement, larger intake ports, and (I think) a better cam than a 216. 20 to 26 % more torque and HP relative to a 216 seems reasonable.

Hoyt