There are no problems with spelling since /p/ is always <p> or <pp>, while /v/ is always <v> or <ve> and <f> in the one word of.
These consonants differ both in voicing and in manner of articulation, one being a stop and the other a fricative. However their places of articulation are close, and they can be a problem for some learners, especially when in final clusters, as in grapes/graves. (I have included these pairs even though they may appear to be non minimal; see the note on the main page.)
Interesting pairs include:
apiary aviaryThe mean density value is 2.2%. The list makes 128 semantic contrasts, giving a semantic loading of 56%.
apiary aviary apiaries aviaries cape cave capes caves carp calve carped calved carps calves carping calving carp carve carped carved carps carves carping carving cope cove copes coves crepe crave crepes craves cuppa cover cuppas covers gape gave grape grave grapes graves grapple gravel grappled gravelled grapples gravels grippe grieve grope grove group groove grouping grooving hap have happing having harp halve harping halving harpist harvest harpists harvests harpy Harvey heap heave heaping heaving help helve hope hove hopper hover hoppers hovers lap lav leap leave leaping leaving leaps leaves lip live lips lives Marple marvel mope mauve nape knave napery knavery nape nave Naples navels nappy navvy nappies navvies op of opal oval opals ovals P V P's V's pack vac packs vacs pail vale pails vales pail veil pails veils pain vain pain vein pained veined pains veins pain vane pains vanes pale vale pales vales pale veil paled veiled paling veiling pales veils pallid valid pallidly validly pallor valour pally valley palter vaulter palters vaulters pan van pans vans pane vain pane vane panes vanes pane vein panes veins paper vapour papers vapours parrs vase pars vase parse vase parses vases passed vast past vast pat vat pats vats pax vacs PC VC pea V peas V's peal veal pease V's pecks vex pee V pees V's peel veal peep peeve peeping peeving peer veer peered veered peering veering peers veers pelt veld penally venally pending vending penned vend perjure verger perjures vergers perry very Persian version Persians versions pest vest pests vests pet vet petted vetted petting vetting pets vets pew view pews views pi vie pick Vic picker vicar pickers vicars pie vie pies vies pied vied pier veer piers veers pile vile pillage village pillager villager pillagers villagers pillages villages pillar villa pillars villas pine vine pines vines piper viper pipers vipers piracies viruses Pisa visa pocks vox pole vole poles voles poll vol polls vols poll vole polls voles Polly volley poly volley polys volleys pouch vouch pouched vouched pouches vouches pouching vouching pox vox purge verge purged verged purges verges purging verging purse verse pursed versed purses verses Pyle vile pyre via rape rave raping raving reap reeve rep rev repeal reveal repealed revealed repealing revealing repeals reveals repp rev repulsion revulsion ripe rive Ripon riven rope rove roping roving sappy savvy serpent servant serpents servants shape shave shapes shaves shaping shaving shipper shiver shippers shivers sip sieve sipping sieving sips sieves sleep sleeve sleeps sleeves sleepless sleeveless slipper sliver slippered slivered slippers slivers spelt svelte steep Steve stripe strive stripes strives tepee TV tepees TVs trope trove viper viva vipers vivas weep we've weep weave weeping weaving weeps weaves wipe wive wipes wives wiping wiving
John Higgins, Shaftesbury, January 2010