On a mild build 340 and converting to mopars electronic ignition system - is it a good idea to have more of a performance advance curve or just leave it stock

also, whats a good timing setting

The MP dist has a pretty good curve factory. I wouldn't make any changes till you have it running and see how it is. Good start point is 15 initial and 38 total by 2500rpm

38 total is a big block number and is little too much for a small block. I would stick to 34-36 total.

The two sb MP distributors I have purchased were set up with 24 degrees in the distributor to go along with 12 initial (set up for a stock engine). Depending on the cam you are using 15 initial or even more may give you the best idle and off idle throttle response. This will require you to limit the mecahical in the distributor. The easiest way is to get the Mallory tuning kit (#29014) also sold under a mopar number. It has spacers to set up the stops and comes with an assortment of springs. As you limit the amount of advance in the distributor you need to go to heavier springs to keep it coming in at the same rpm. When you get down around 20 degrees in the distributor two orange springs or one orange and one brown work well fro a street driven car (all in around 2500 rpm).

find the ideal initial for your eng/cam then with that figure in hand shorten the slots the required amt(may take several tries and the chart is in the archives)to get 35 total(vac adv disconnected)then playw the springs(light as possible staying just under pinging @ WOT) thenhookup your vac adv & adj it staying just under pinging @ PART THROTTLE