With a week gone by and no answers you might think you should have showered first.
I don't have a good answer for you and I suspect that's why no one else has responded either. I've not heard of anyone hot rodding a 228 or 248 since the 270 and 302s are enough bigger to make a big difference, and they aren't that hard to find.
As far as I know the external parts that fit the bigger jimmy motors will also fit your 228, but really I'm only guessing.
I'd watch ebay if I were serious about finding GMC performance stuff, but I'd expect it to be old and expensive.
