See item 125 which addresses the O-320B2B on the 7GCBC and refers to Note 13 [emphasis added]:
125. Lycoming O-320-B2B engine (Models 7ECA, 7GCAA, 7GCBC) Installed per Champion Dwg. 7-1289.
Requires aircraft to be outfitted per Note 13 (7GCBC) or Note 15 (7ECA, 7GCAA)
Fuel 100 minimum grade aviation gasoline Engine limits Maximum Continuous 2700 r.p.m. (160 h.p.)
Oil capacity 8 qt. at –36 Required equip.
Landplane: 20(a), 102(f), 103(i), 117(e), 123(a), 201(i)(l), 202(g). Modifications per Champion dwg. 11-1029 (7ECA only). Original Equipment Serial Numbers: 400-97 and up (7GCAA) 1200-94 and up (7GCBC)
----
NOTE 13. The following changes apply to 7GCBC aircraft built in 1994 and later (all with 7-1545 wings).
C.G. Range and Maximum Weight changes apply to any 7GCBC that retrofits with 7-1545 wings except for airplanes with optional engine item 122.
C.G. Range: Landplane: (+14.2) to (+19.2) at 1800 lb. (+10.5) to (+19.2) at 1325 lb. or less
When performing acrobatic maneuvers, the C.G. range shall be limited to: (+14.2) to (+16.3) at 1800 lb. (+10.5) to (+16.3) at 1350 lb. or less Straight line variation between points given.
Maximum Weight, Landplane: 1800 lb.
Serial Nos. Eligible 1200-94 thru 1202-94, 1203-95 and up
For Serial Nos. 1360-2004 and up with optional engine item 126 or 127; when performing acrobatic maneuvers (see Note 10) the airplane must be loaded as shown above. The airplane may otherwise be operated in the Normal category as shown below.
C.G. Range Landplane: (+15.4) to (+19.2) at 1950 lb. (+10.5) to (+19.2) at 1325 lb. or less Straight line variation between points given.
Maximum Weight, Landplane 1950 lb.
Required Equipment Item 126 or 127
----
The 7-1545 wings mentioned above are the metal spar 7GCBC wings, introduced in 1994.
Item 122 addresses O-235 engines (i.e. no gross weight increase for a 7GCBC with metal wings and downward powered O-235 engine.)
Items 126 and 127 are 180 hp O-360 engines.
----
*My* read on this is that in order to install a 160 hp O-320B2B, you do not need metal spar wings, you just would not get the gross weight increase to 1800 pounds noted in Note 13.
That said, the wording "Requires aircraft to be outfitted per Note 13 (7GCBC)" is a little ambiguous and I can see where the reference to Note 13 and that initial wording could be taken to mean that metal spar wings are required. The question would be "Does it mean it must have metal spar wings (and not just any metal spar wings but the ACA 7-1545 wings) or does it mean if not equipped, it doesn't get the 1800 pound gross weight increase? However, since Note 13 is all about metal spar wing gross weight increases and new CG limits, I think it's actually silent on the issue of "requiring" metal spars for the 160 hp engine installation. And that makes sense as the Vne isn't increased anyway, and other than Vne and gross weight, the wings have nothing to do with the effects of a 10 hp increase in power. If there was an issue it would be in terms of the engine mount and fuselage being stressed for 10 more hp, and that issue isn't raised anywhere, even with the 180 hp installations.
Consequently, *my* read on it is that the 7-1545 wings are not required for the reasons noted above, plus the fact that any ambiguity in federal regs and documents goes against the author not the reader (based on 12 years of reg writing and enforcement experience).
However you'll need to find an AP / IA who agrees with that interpretation and will sign off on it.