I’ve wanted to do the same thing with my 350/700R4 in my 69 to. I just met a guy who stabbed and LS1 into his 89 Camaro, sounds to complicated with the knock sensor chasing, etc. I told him if I did that to my 69 it would be with an LS3 package with the transmission. It’s a plug and play set up.
I installed a Holley Sniper on mine for now and I’m very happy with it. I understand the good old small blocks.

 

I'm sure the 200-4R could work well with an LS engine, but I feel some of the magic of an LS swap is the ability to have excellent tuning capability of both the engine & transmission together.

The 200-4R does have a much better gear ratio spread than a 4L60E & is much lighter than a 4L80E, so I can see your desire to keep this trans.

How was the install of the Holley Sniper ? im looking into it now. Did you need to do electric fans ?

I have to agree about the tunability with the 4l80e 4l60e. Not 100 % sure that to do kind of leaning towards doing Holley Sniper efi for now

 

I'm sure the 200-4R could work well with an LS engine, but I feel some of the magic of an LS swap is the ability to have excellent tuning capability of both the engine & transmission together.

The 200-4R does have a much better gear ratio spread than a 4L60E & is much lighter than a 4L80E, so I can see your desire to keep this trans.

 

I went with a carb on my LS since I had nothing as for the fuel injection, just a long block.
Had my TH350 done up with a bigger stall and a forward full manual valve body....works great. Would be nice to have OD.... but not enough return for the investment to me.
FI would be nice though

 

My Sniper is great! Super easy to install, I used an in tank fuel pump with a new as tank to save time with a return line. Fool proof setting up with the screen prompts and you can taylor it to your specific needs. About the only thing I would’ve done different is to run hard lines, I went with steel braided lines but I feel hard lines would’ve been a cleaner set up.

Now for the power, super crisp compared to the old Edelbrock carborater. It feels like you have all your hp working at all rpms compared to the lag of a carburetor. Went with the Holley over the FITech because it’s made in America and their service is second to none! I’ve heard many stories of guys having to send theirs back to the factory if they’re is a problem.