Changing from a th400 to a 4L80E

Ok, here is how it is. I've got extreme body damage on my 91 V2500 4x4 Suburban which has a 4L80e Tranny. I bought a 1989 V2500 4x4 Suburban with a th400 tranny to replace it. I want the 4L80E tranny of course. I need to find the best way and lowest cost to use my 4l80e. I could spend 1,200 bucks and get a stand alone compushift pcm. Is there anything better instead?

Also, I currently have bucket seats but, they are the stock ones and they are not what I want for off road. What kind of seats or what kind of vehicle should I get them out of? Remember, this is my recreation vehicle so, I dont have much *** to spare for interior and other non-priority items.. I am focusing my dollars on mechanical items..  
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Strength before Comfort..
1991 V2500 Suburban 4x4 5.7 14 bolt 4" up 35" BFGs 4:88's manual lock
Built 'OldSchool Chevy Tuff!!'

i dont see how your going to get out of buying a stand alone computer for the 4l80E ......the older suburban dosnt have the neccesary computer for it....and u cant run the 4l80E mechanically...... but can i have your th400    jk .....  
solid axle chevys cant be beat
78 K5: 350 V8,700r4,np208, 8 lug D44 4:88, 14 bolt 10.5 4:88 with detroit locker and 35 inc parenelli jones dirt grip tires

hey thanks for the input Geo. I think that I am going to buy a stand alone comp for it. I was looking into Compushift and a couple of others. Any recommendations?? I do believe that they make something that CAN make a 4l80e mechanical somehow. that would be amazing...... Also, I dont know how it can be done but, they have stand alones that can turn a 4l80e into a five or six speed. I think that it uses overdrive between your lower gears.. Weird\amazing... Man, where is Wyjax, he knows everything...  LOL
Wyjax, if your there, I can use your input...  
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Strength before Comfort..
1991 V2500 Suburban 4x4 5.7 14 bolt 4" up 35" BFGs 4:88's manual lock
Built 'OldSchool Chevy Tuff!!'