If you want to speculate on a bottom in the hard-hit homebuilders, buy Pulte ( PHM), Jim Cramer said Friday on CNBC's "Stop Trading!" segment. Cramer said the speculation that billionaire Warren Buffett is looking at the sector isn't "nutty," but he said investors hoping to play a possible Buffett deal should buy Pulte, which has a national focus, rather than Hovnanian ( HOV), which is more of a regional player and therefore less likely to be of interest to a big-picture guy like Buffett. Cramer stressed that he isn't recommending any of the homebuilding stocks, nor would he short them. He said Friday's big rally in KB Home ( KBH), Beazer ( BZH), Lennar ( LEN) and Centex ( CTX) shows how hard it is to make a play in either direction on these stocks, whose fundamentals remain poor with house prices slipping and inventory rising. Cramer also said it's time to buy Grant Prideco ( GRP) in light of Friday morning's comments from GE ( GE). "It's time to step up," Cramer said.