I personally do not have any at this time . It also depends on what you call a "giant tomatoe " . Did you want giant plants then I recomend "tripple climber" 15 feet plants, giant vegetable then "megatoms" or they used to send seeds from the Jersey giants winners for postage and handling . Look these up on the internet.

Here's the biggest I've ever grown:

{{gwi:839659}}

Sadly, this year I was unable to find my seeds saved from last year, so it looks like the end of the line for the genetics of my garden tomatoes, barring volunteers. :P

You can get seeds of a variety called "Delicious" from Tomato growers supply or rareseeds.com or other places. The biggest tomatoes are frequently grown from delicious seed.

The world record Delicious was a freak of nature to never be repeated,at least not by a Delicious.For giants I'd go with Big Zac f1 the only hybrid I'd suggest. Now if you want to save your best seed and try to improve it every year I'd suggest a heirloom such as
Giant Belgium
Brimmer
Phil's Fantastic
Old Colossous

There are several.Than look for a super Bloom which is more than one flower together. I got a 5 way bloom in my garden right now and I'll put a pic on here but it's blurry.I can't seem to get the pic on here but when I figure it out I'll get it on here.

Here is a link that might be useful: