You should be looking at 66" tubs or 72" tubs. But this is not a simple replacement project. It's a complete bath redo, and you'll need to budget to replace most of what exists currently. Where do you plan to carve out the additional room needed from? Is there a closet at the end of the current tub? What about the width? Longer tubs are also usually wider. That may mean that it will now be too close to the toilet or vanity. Do your guys even actually use a tub? Or do they prefer to to shower? Might a larger shower only be more functional?

Post a layout drawing for better suggestions as to how to fit in what you need here.

Thanks for the thoughts. Yes, we are a bath family. The boys like to relax or 'swim' in the tub. We are squaring off the back of our house and gaining 10 ft in the bathroom. So it will be a complete gut job with all new fixtures.

Are you planning a standard alcove tub just in a longer size or are you looking for something more along what you see in most jetted tubs (but without the jets)?

If you're looking at longer standard alcove style tubs, you will need to compare the basin sizes as well as the overall tub size. It is amazing to me that tub manufacturers make 66" tubs and they put all the extra length into a ledge at the back of the tub instead of adding it to the actual basin/bathing area. Additionally, the upcharge for that non-standard size alcove tub can be pretty steep for not alot of extra space.

If you're looking for more of a jetted tub style without jets (AKA a soaking tub), look for one that is not only long but deep. Those tall men in your house will appreciate being able to sit in the tub, fully/almost fully extend their legs and not have half their torso sticking out of the water. This is the route I would take as it provides the most length, width, depth, installation, and shape options. We have the Kohler Purist in the oval shape with the overflow feature for maximal depth and love it--you may want to check it out.
Hope this helps!

Thanks very much for the great Ideas

You really need to focus on interior dimensions. There are tubs that are 60" long that have as much space as 66" or larger length tubs. But you also need to understand the volume of water the tubs hold and ensure that you have enough capacity in your hot water heater to fill it to an appropriate level.

Once you get into the realm of longer tubs, things can start getting more expensive, so you'll need to watch out for that, too. I ended up with a Mirabelle Edenton, which was mid-way between the Kohler price point and the Hydrosystems/Bain/MTI price points.

I have a Hydro Systems Lacey in 66"x30"x20". My significant other is 6'3" (so shorter than yours) and he fits fairly well and can soak (and does). I also considered a Kohler Archer, but went with the Hydro Systems due to shipping time. I love the tub and would do it again or if I could fit it, the 72"x32" version. It does put a strain on our water heater, but the size makes it actually usable for us. Previously we had a standard 5' tub and that simply did not work for either of us. (Though it was great for bathing the dog.) I opted for a model without jets and it's great for taking a deep soak.

We had a similar requirement - DH is 6'6" and for that reason hates to lay in the tub, he always feels squished. But with back problems, etc I wanted to get a tub he could easily fit in.

We went with a "sitting" tub - google ofuro. We wound up with the V & A Sorrento, and also had a tankless heater put in to supply it. We love it - it's soooo comfortable.

Go online and enter plumbingsupply.com. Then look for brand name Americh; style Malibu. It's a soaker tub 84" x 66".

plumbing supply.com. Made by Americh; style Malibu. Dimensions L= 84" x W= 66" x H = 22". They have many other large soaker tubs to look at.