adding ground wire for oven install
I am soliciting an advice on how to best solve this problem. We are in California (LA). We are replacing a very old double oven with a new single oven. The old oven was rated 40 amps/240V and was installed correctly (back in the 70s I am assuming) with the right gauge wires and it was a 3 wire install - two hot/one neutral. The new oven has a 4 wires (2 hot, neutral and ground) and the manual explicitly says that "where code allows, 3-wire install is aacceptable). Oven is rated for 30 amps/240V.
Q1. Circuit/junction box is not being moved - we just have the junction box in the wall and the new oven is going into a new cabinet built to accommodate this new single oven. Does California/LA code allow grandfathering of 3-wire installation?
Q2. Regardless of answer yes/no to Q1 - we would like to upgrade to 4-wire eventually. Is it possible to pull additional wire through that conduit (it is a flex metal squidy looking) to make that wire the dedicated ground? We can't really afford to pull a new conduit, our service panel is full and replacing or adding a subpanel is a major expense.
I tried to search through discussions on this site because the question of 3-wire vs 4-wire install comes up often but I got lost and confused. We will hire an electrician to do this of course - I just need to understand the options upfront and make an informed decision on how to proceed.
I really appreciate everyone's advice.