What size range are you buying?

The insert size needs to fit the whole alcove area. Not just a tiny bit above the cooking spot. That’s a very expensive look for a lot of reasons. You’ll also need engineered make up air.

I am purchasing a 36inch range and need 900 CFM. My handy man who will be installing the vent liner thought I needed a different style liner than the vent a hood I was considering.

How big is the alcove? How high above the range is the lowest spot? How deep is it front to back. If you get a smaller insert, the custom stainless liner still needs to be a full 24” depth and entire width of the alcove.

OK, again to the barricades ...

You size the intake aperture (the hole that leads to the baffles), whether it has a wood overlay or a stainless steel overlay, or a copper overlay, to capture and contain the rising and expanding cooking effluent plumes. This usually means overlapping the cooking zone by a few inches on each side. In this particular case, if you don't mind the entire area being a hood and accumulating grease, then overlap is achieved, but I don't recommend approaching the plume expansion this way. Just make the insert large enough and the rest of the volume will stay clean.

Having sized the overlapping intake aperture, then determine required maximum volumetric flow rate by multiplying the intake aperture area (in square feet) by 90 ft/min to find CFM.

Next, account for pressure losses in baffles, hood transitions, and ducting, plus, imperfect make-up air (MUA) pressure balance. If you don't know all these often unpublished parameters along with the blower's fan curve, multiply the required CFM by 1.5 to find rated CFM for the blower. This approximation has a good chance of being sufficient for residential hood and liner designs.

Duct area should yield 1000 to 2000 ft/min air velocity at the required CFM.

MUA is needed for the hood to work. If it isn't provided by house leaks (and I don't expect 600 or whatever CFM of leaks to be available) and if opening windows won't pass code or winter conditions, then a deliberate MUA system is needed, either passive (no blower) or active (with blower). How well the MUA must make the house interior pressure match the house exterior pressure depends on several factors, the most important for safety being the presence of combustion appliances taking air from inside the house. Read various MUA related threads here for more information.

I have 80 inches to the ceiling. Plan do do 40 inch liner. Looking at vent a hood (BH249PSLD) or zephyr Monsoon II. Is there any reason why either of these would not work with the wood vent cover?

Also I plan to have the MUA issue addressed as well.

Interface and physical data for these candidate inserts needs to be given to your builder or architect to determine compatibility with your structure.

A 40” insert is not nearly large enough for that type of setup. The entire thing needs a custom created to fit, stainless liner, to cover everything under the cabinets. Then a bigger insert is incorporated into that.