Sounds reasonable to me. my NA Supras got beat by dodge daytonas and fully laden work vans. The one I gave Clayton might change your mind, but it's thirst for AVGAS didn't belie it's 12.x:1ish compression either.
You are, however, wrong in displacements. 1978 had the 2.6 liter carbbed 4M, with a really poor fi system in late 1981 (4ME) (But then again, there were like 800 of those). the 5MGE in the 1982-1986 Supra was 2.8 liters with 145 claimed hp (but dynoed very close to 200 with cali emissions)(Oddly enough, the MR2 was rated at 145 and also dynoed out closer to 200). The 3.0 7MGE ran poor harmonics and focused heat on valve heads and the piston dome. Outside of that, it was like a 5 or so real hp gain. the 2JZGE was rated at 225, and dynoed at about that all day long. But that's a totally different motor than the M series.
the 22R was 2.4 liter, the 20R was 2.2.
All kidding aside, the Supra's balance, gearing and engine was a good 20 years ahead of it's time, and I will take the pepsi challenge against most cars with a second gen Supra (Enjoyed far more than my 3rd gens)