My wife has a Richmond 5 speed in her 73 Camaro. To me it's about as hard to shift as a Muncie 4 speed, maybe a little bit stiffer. It got a lot easier to shift after some break in miles, we use regular non-synthetic oil. Mary loves it and has no complaints, but the shift effort is more than a T56. We have the Hurst shifter which is probably easier to shift than the Long shifter, the long has a shorter stick.
I love the closer gear spacing of the Richmond, but it MUST be used with a 3:08 rear gear or taller. I drove a BB Chevelle with a Richmond and 3:73 rear gears the gears were WAY too close and close gears are not needed with BB torque. You really feel this when just loafing along from a stop light and you are rowing through the gears just to get up to 65 mph. I think the Richmond is more suited to a small block, especially a higher revving small block.
I have been told they are not as strong as the other choices out there. The Richmond has a 450 foot lb rating. This is probably a conservative rating allowing the trans to last many many miles. It does lack support of the gear train in the center which is where failures are reported. The main case splits in half so it's very easy to work on. 5th gear ratio is 1 to 1 so the drive shaft is not spinning faster than your engine.
With your hp and torque, I'd look at a Tremec or T56, especially if you want to do hard drag launches. Common performance gearing for the T56 is 3:90, but you may want to gear a bit lower numerically.
Here's a gear chart I did for our Richmond to plot shift points and rpm drops. Follow the chart to your shift rpm, then draw a line down to the next gear to read your rpm's you will be at after the shift.
FYI, a new Richmond is around $1900. The Hurst shifter is another $300, plus shipping and tax, then add a new yoke.
Here is a tremec for comparison. I did this chart a few years ago, so this isn't the newest Tremec model. Verify the gear ratios of whatever Tremec you are considering.