Those are about as good a battery as you'll get. A member here spent about 2 years testing LiPo batteries and CNHL was right near the top. Only ones better were expensive drag packs meant for extreme loads.
CNHL is always having huge sales. Check out the 6600mAh 3s batteries here. Dirt cheap.
https://chinahobbyline.com/collections/cnhl-flash-sale/products/flash-sale-for-us-warehouse-03-26?variant=45146995294422
You will have to solder a different connector on the battery.
https://chinahobbyline.com/collections/cnhl-rc-car-batteries/products/cnhl-racing-series-6200mah-11-1v-3s-90c-lipo-battery-with-ec5-plug?_pos=17&_fid=44741f95a&_ss=c
But these are on sale...
5000+mAh and at least 60C. The higher the C rating the better for anything that goes fast. Look at CNHL. They usually have some good sales.
Really good looking truck you got there.