These blocks for MBX8 are narrower than stock C and D blocks, and allow you to use MBX6 arms (E0150) which are longer than mbx8 arms. Making the rear of the car more controllable, and absorb bumps MUCH better.

TDM tuning blocks is what the Big names were using on their MBX8 buggies prior to the MBX8R being released. Direct fit using Mugen MBX8R arms

MUGE2183 or MUGE2171

Other options - Using AE arms
ASC81435 - RC8B3.2 FT HD arms
OR
ASC81434 - RC8B3.2 STD arms
ASC81194 - narrower shock end and balls to fit AE arm (narrower pocket 6mm vs 7.7mm)
ASC81197 - shock retainer pin like the MBX8 but smaller to fit AE arm
ASC81150 - Anti-Roll bar kit - for sway bar link end so it fits AE arm (narrower pocket 6mm vs 6.7mm)