170 or 225?

Two things when building small displacement rpm and gearing.
And really the 225 is really small engine in the first place.

Rpm shouldn't be a big problem unless your looking to build a 300+ hp engine. Should have to spin the 170 about a 1000 rpm higher to reach the same power as the 225.

2nd and probably the most important is gearing. To put the same torque to the ground and to put the 170 in the powerband.
You'll need to go about one full ratio deeper.
So a 3.55 225 = 4.65 170.

Sure you can run 3.55 in both. But 220 hp 170 is not gonna keep up with a 220 hp 225 and no chance with a 220 hp v8 if all running 3.55. Thats why people spend big bucks to gain 50 + cid and you can practically for free.

My rule for small displacement is if your willing to gear it build it. If not go bigger or except the lesser performance.