Congratulations on the engine swap! As far as the plugs I would leave them as is until I had the carb all dialed in with jetting and power valve selection provided they are firing ok. I don't have exact plug numbers for the 292 in front of me but an R45XLS or an R44XLS sounds about right. If it helps any: R = resistor type, 44 is the heat range, XL = extended reach ( long threads , S = supressor tip. The 44 is one heat range step cooler than the 45. Also be aware that AC Delco has dropped some plugs out of production and use a single number to replace 3 or more of the older numbers.
I'm sure that 292 woke your Malibu right up! Enjoy.
