Originally Posted by AF
Axles and a clutch would be good, yes. B-Series transmissions can handle huge loads of power.
At 300HP, I'd probably do sleeves and rods...pistons will still be fine most likely.
Sleeves would be considered much farther down the road. The stock sleeves will easily hold up and should be considered after the stock pistons or rods have been upgraded.
The strength of the stock sleeves is very dependent on the tune. I have seen tunes that allowed stock sleeves to be ran reliably on 600-700 whp setups.