Re: F250 vs F350 Rear Leaf Springs
All F-350 SRW and many F-250 have the same Code "B" rear springs. But some F-250s have the weaker "F-250 Code A" rear springs.
Both will fit nicely.
Your spring code is on the lower door post behind the driver's door. It will be a two-character code, with the first character being the front springs and the second the rear springs. Yours is probably "VA". Ford put the code "B" rear springs in F-250 around the 2001 and 2002 model years, but I don't think they did that for your '99.5.
My Sierra Blanca in the sig pic was a great pickup for 11.5 years. I sold it a coupla years ago. I drove a hand-me-down 2003 F-150 SuperCrew 4.6L 2V for a while, but it was unacceptable for towing more than a rowboat. Replacement is a 2012 F-150 EcoBoost SuperCrew Lariat that tows my 5,000-pound TT like a dream.