I need to know if a th400 can be swaped with a 7oor4 if they both have 241 t-cases

Heres my delema

I have a 91 K1500 the engine has been swaped to a 98 L29 big block with a large cam,headers and Accel DFI.It's not making enough vacumn for the th400 to shift right.

Now in the past this thing burned up 700r4 tranys,I think mostly because of insuficient cooling.Stock the engine put out 310 hp 410 torque,with the can and tuning I can't emagine that it added a 100 to those numbers.Shouldn't a 700 be able to hold that much?  

do you have an adjustable modulator?

if it does take the adjustment screw out completely for high shifting and seemingly not enough vacuum, If that doesn't work there are other problems...shifting to low will require the screw to be turned in a couple turns...

the 700 will haqndle the powere, but you'll have to regear the axles to make it live.  

Most 700R4 burn up because gears are too tall and it rides the converter stall a lot and slow bakes. The 700R4 gets in "trouble" because it has a much deeper first gear than a THM 400 or THM 350 and it can still start out well from a stand still if with tall gears. THe problem is that when you get into drive and OD it rides converter stall and lot and cooks. If you run say 4.56's with 33's and 4.88's with 35's or 36's and 5.13's with 38's, you should not have any problems with tranny. Those numbers might sound deep but a 5.13 with a 700R4 has a effective final drive ratio equal too a THM 400 with about a 3.54 yet the 700R4 with a 5.13 will have a first gear over all ratio of about 15.8 to one vs 8.8 for a THM 400 and a 3.54. In more simple terms, you will have 80% more wheel torque in first with 700R4/5.13  vs THM400/3.54 yet same cruise RPM. Have you seen the light here??  

So basicly after spending $2000 or more to swap out to a 700r and change the gears all I will gain is off the line torque.  

You will gain much more wheel torque in first, second and third and gain a extra gear too. You will have like a "granny" of sorts in that when using the comparison above, a 700R4 with a 5.13 would have a over all effect ratio of 8.1 to 1 in second vs 8.8 to one with a THM 400 in FIRST and a 3.54. Also I might mention, a THM400 and same as above mention ratio (used for same cruise RPM in top gear) you over all effective ratio in reverse is about 7.4 to 1. With a 700R4 and a 5.13 it is about 11.3 to one. Many over look the beauty of running a 700R4 and being able to run some seriously deep gears and increased your effect gear ranges AND still cruise nicely.  BTW, on price, you should be able to pick up a set of quality gears (front and rear) on line for under 500 buck delivered and if you shop around get them installed for 400 to 600 bucks if you farm it out.