CLINT EASTWOOD will take a “Chainsaw” to daughter Alison’s marriage if new hubby doesn’t “make her day” with a fully loaded pre-nup!

t Eastwood’s family will make sure the fortune is protected by an airtight prenup before his daughter Alison’s March 15 marriage to “Chainsaw Gang” star Stacy Poitras.

The 45-year-old wood carver – who leads a foursome of beer-swilling rough­necks at Deadwood Tree Sculptures – has dated Clint’s 40-year-old actress daughter for five years.

ALTHOUGH THE CRUSTY screen legend agreed to give his daughter away to the reality star, it won’t really make his day, suspects a close source.

“I bet Clint will insist they sign an ironclad prenup so that when Alison finally wises up and dumps Stacy, he can be absolutely sure his millions are protected,” said the source.

Although Stacy carves out a pretty good living with his TV show and artwork sales, Clint will want to “make sure he will never be able to take the entire Eastwood family to the cleaners,” added the source.

After Alison – Clint’s daughter with first wife Maggie – and Stacy announced their engagement last year, they looked forward to plan­ning a lavish wedding in Carmel. But perhaps due in part to Stacy’s embarrassing antics – and Alison’s friends begging her not to go through with it – they decided instead on a low-key, intimate wedding in Calabasas, Calif.

During the engage­ment, the source says Stacy rubbed his future father-in-law the wrong way, like when he kept saying he was engaged to “Clint Eastwood’s daughter” instead of “Alison.”

“In my opinion, Stacy is only after fame and money and to promote his show,” charged the source. “But I bet Clint sees right through him!”