Lockup in 1st and 2nd manually

[Smokin ACE]

I swapped a built 47rh in my 1st gen a few months ago. I've got to say its the best mod yet. It has a bilet flexplate, billet triple disk converter 2200 stall, billet input, steel 5 pinion planetary, custom valve body, and some other upgrades. Right now the truck will lockup when I have it in drive 2nd through Overdrive. I truck pull with the truck and have done one pull with it since the new trans. I've decided I need to be able to lock it up in 1st and 2nd with it manually in those gears instead of being in drive and let it shift up. I think thats the only way I will be able to keep my rpms up with the VE pump pulling for this season til bigger plans later on. I will probably only use lockup in those gears for pulling as I know it can tear stuff up. I've heard you can get custom valve bodies that will allow this, but I don't want to spend the money since it already has a custom modified valve body. I was thinkin of droppin the valve body myself and doing whatever you got to do to allow it to lock up in 1st and 2nd if I know what to do. This may be a big secret to the trans builders out there, but if someone knows what to do that'd be great and save me some time and grief. So what do I need to do? is it as simple as drilling a few holes in some passages or do i need some hard parts as well? Thanks