J head 1.88 vs 2.02

IMHO I would switch to the 2.02s now while things are apart. They will flow better and offer more potential. Then, if you decided to put in a bigger cam, manifold, carb, etc later, you would not have to pull the heads off and drag them to the machine shop. Can you get by very satisfactorily with the 1.88s? Yes, but I'd go with the 2.02s. They put them in the 340 for a reason. Again, IMHO.