kind of a tricky situation with the dogwater compression. but you have gears and a converter... however with the weight of the car that throws another wrinkle into the mix.
a shoot from the hip would say melling spd-22, summit 6900, 6920 & 1789 all kinda fall into that 340 or 340 adjacent category.
melling 23103 would be an interesting choice and probably make gobs of torque.
i *really* like howards steetforce 1 in this application, but that's a lot of bread.
i think anything that's got under 270 and less than 112 lsa would be where i'd be looking. especially if it's just a stop gap while i had the roller core reground.