Atf fluid for A-518 transmission.

hello everyone, i have a 1991 dodge power ram 150 short bed 4x4, its got a 360 magnum and the A-518 automatic transmission. I just recently had the transmission fully re-built and the builder told me to flush all the atf out of it at 1000 miles and change the filter. I asked him what type of fluid should i put in there and he said we put +3 in it, but he says its hard to find +3 anymore we get it in drums from amalie. I said would +4 be ok to use? and he said i wouldnt run +4 in that transmission because you have a non lock up converter and +4 has alot of friction modifyers in it to make a smooth engadgement into lock up .
He said you could run +4 by all means if you wanted too but its going to make your trans slip while shifting and make it run hotter.
He said if you can bring it to us and we can service it with +3 or if you wanna do it on your own you could use dexronIII, and he said in fact dexronIII was used as factory fill the A-518s from 89-93 mopar type 7176 fluid did not come out untill 94 and thats because they made the A-518 into a more electronically controlled transmission with lock up that engadged with a spped or rpm sensor and he said they would lock and un lock and dodge realized dexronIII could not handle the heat of the converters going in and out of lock up and it was eating the converter clutches, he said if you have non lock up A-518 made from 89-93 dexronIII is fine to run it.
So after that chat with him i decided to do my own research regarding this and found out that he is pretty much right, i have talked to several people online who run type f atf in the non lock up A-518s and dexronIII and even the new dexronVI, the new dexronVI is backwords compatible and can be used in any transmission calling for dexronIII just like +4 can be used in +3 applications, except im told dexronVI does not have as many friction modifyers in it as +4 does hence it allows for firmer less slippery shifting and being that it is a synthetic it handles heat and can go alot longer. My old man ran type f in all of his mopar 727 transmissions and it worked great, he ran type f in his 70 plymouth cuda with a 440-6 pak and ran type f in his 75 dodge truck with no issues.
Like i said i have talked to a few people who run type f in the A-518s and love it and they say it works well for them as well as the people that i have talked to that are running dexronVI.
With all that being said i have narrowed my choices down to type f or dexronVI, i am going to use one of those fluids after i flush the +3 out at 1000 miles and change the filter, i would run +3 if it was available, but im not over paying for it at the transmission shop, im sure there will be people who will try and say i have to run +4 but no i dont, i have done my homework on this topic and have found out that type f dexronIII and dexronVI will work and will work better then +4 since they lack the friction modifyers +4 has, so with that being said what fluid would you guys reccomend out of type f and dexronVI? i realize with the dexronVI i will be able to put more miles on the fluid, and get better heat protecting ability and shear protection, but on the other hand it is pretty expensive.
Then there is type f that is very affordable and it will provide the firmest shifting with less slippage them dexronVI therefore making it last longer and run cooler as well, down side to type f is that it has to be changed more, it lacks the additives that dexronVI has so the type f fluid does not last as long therefore needs changed more often..... Well thats the delima im facing between type f and dexronVI so wich fluid of the two would you guys reccomend?

I did not have time to read the entire post, but type 4 replaced type 3 so you should be able to use it. I have an Intrepid right now and it says 3 on the dipstick, but I'm running 4 in it cause you can't find 3 anymore and it works just fine.