AFTER DATING for eight months, Tom Cruise and galpal Penelope Cruz have decided to tie the knot — and hope to get hitched before the end of the year, say delighted pals.

Tom, 39, and Penelope, 27, have already began house-hunting in upscale Greenwich, Conn., where they can rub elbows with such stars as Mel Gibson, Diana Ross and Kathie Lee Gifford.

Beautiful Penelope — who was raised Catholic — has paved the way for a happy marriage by making several trips to the Church of Scientology’s Celebrity Center in Hollywood to take courses at Cruise’s behest.

A devout Scientologist, Tom wants to make sure that there won’t be any religious friction between the as there was between him and second wife Nicole Kidman.

“Tom is telling pals he’s certain his marriage to Penelope will last ‘forever,’ ” revealed an insider. “He’s been wooing her nonstop for months — and she’s moved to Los Angeles to be near him.”

When Tom recently popped the question, the thrilled Spanish beauty readily agreed.

“Tom proposed one night at the house they’ve been sharing in Beverly Hills,” confided the insider. “Not much was said, Penelope guessed ‘yes’ — and that was it.

“There have been a few details to work out, but expect a big party before the end of the year.”

Among those “few details”: a commitment from Penelope to become involved in Tom’s Scientology religion and a prenuptial agreement.

“He’s expecting to pay out a pretty penny to his ex-wife — about $30 million,” noted the insider. “And the Scientology issue is near to Tom’s heart. Nicole’s lack of 100 percent commitment to the Church of Scientology became a huge issue in their marriage and, ultimately, their divorce.

“She didn’t want to raise the kids as Scientologists, while Tom was adamant they be raised in the church. But Penelope told Tom she loved him so much shed be happy to consider joining the church.”

Tom is chafing at the bit to marry Penelope — but she thinks it’s still too soon after his divorce.

“Penelope is an old-fashioned girl, and out of respect to Nicole she wants to wait a little longer,” divulged the insider.

“She thinks there should be more of a cooling-off period before she and Tom wed.”

Meanwhile, they’ve been looking for new digs. “Most recently they’ve been house-hunting in Greenwich, Conn.,” revealed the insider.

“Tom and Penelope are also discussing the where and when of the wedding, and how big or small to keep it, and who to invite.

“Penelope’s truly walking on air — she can’t wait!”

Added a source close to Cruise: “Tom is very much in love with Penelope. He feels certain that his relationship with her will stand the test of time.

“As far as marriage is concerned, he believes wholeheartedly that the third time will be the charm.”

Penelope is proving to tom that she can make the marriage work, said another source.

“She’s begun visiting the Scientology Celebrity Center in Hollywood. Tom wants her to truly understand his commitment to the religion.

“Penelope will do whatever it takes to make Tom happy. She considers it part of being the new Mrs. Cruise.”