-Deck – Loaded Vanguard Flex 3 – 174 USD
https://loadedboards.com/vanguard-longboard-skateboard/
-10S2P Dual Belt Drive KIT from diyeboard.com – 400 USD
http://www.diyeboard.com/10s2p-battery-esc-dual-motor-belt-drive-power-truck-kit-8352-p-611.html
(Battery/ESC/Motors/Plastics kept, while Motor Mounts/Pulleys/Trucks replaced with the following ones below)

The Chinese KIT rebuilt as Boosted Board Equivalent – to adjustable power belt system:
-New Motor Mount 100 EUR (for the 2 pieces)
https://eskating.eu/product/electric-skateboard-motor-mount-aluminium-carbon-pro-2x/
-New Pulley HTD5M 15T / 16mm – 7 USD (2 pieces)
https://www.aliexpress.com/item/2pcs-HTD-5M-15T-Timing-Pulley-5-6-6-35-8-10-12mm-Inner-Bore-16mm/32790573928.html?spm=a2g0s.9042311.0.0.7f9f4c4dXtUZ7N
-New Kegel Pulley HTD5M 36T/12mm – 44 EUR (for the 2 pieces)
https://eskating.eu/product/htd-5m-363840-teeth-nylon-carbon-kegel-wheel-pulley/
or you can print from STL file:
https://www.thingiverse.com/thing:1711107
-New Timing Belt HTD5M 265mm/12mm – 14 USD
https://www.aliexpress.com/item/POWGE-265-5M-Synchronous-Length-265mm-W-12-15-20mm-Teeth-53-HTD-5M-Closed-Loop/32635385264.html?spm=a2g0s.9042311.0.0.7f9f4c4dXtUZ7N
-New Orangatang Kegel Wheels 77A – 50 GBP (4 pieces)
https://www.skatehut.co.uk//brands/orangatang/orangatang_kegel_80mm_longboard_wheels_pack_of_4_blue_77a.htm
-New Bearings – Bones Red – 15 GBP (8 pieces)
https://www.skatehut.co.uk//brands/bones_bearings/bones_reds_bearings_8mm.htm
-Caliber 10″ Trucks V2 50 degrees – 60 EUR
https://eskating.eu/product/caliber-ii-trucks-50-10-blackout-x2/